DCC Tools

Many tools provide a plug-in capability, allowing them to be extended to provide output in the format.

Mesh modeling

3ds Max: Windows only; commercial. Among survey respondents, 3ds Max was the unanimous choice of commercial tool for object modeling with Ogre.
AC3D: Windows, Mac, Linux. Commercial but cheap at $59.95. Good for static mesh modelling, doesn't support animation.
Blender: Windows, Mac, *nix; free under GPL. Blender is an open source modeling tool, with many advanced features and a very active and dedicated community. The GUI needs getting used to, but lends itself to a very efficient work style once learned. The Blender Tools page describes the many tools available for incorporating blender into your Ogre content creation process.
Maya: 'Windows, Mac, *nix; commercial.''
MilkShape: Windows only; commercial but very cheap. MilkShape is quite straight-forward to use, and supports polygon modeling, texturing and skeletal animation. At time of writing, MilkShape is offered under a $25 shareware license.
SoftImage XSI: Windows, Linux; commercial. Another great modelling tool. Part of the official Ogre development is being done to support this tool.
Wings 3D: Windows, Mac, *nix; open source. Wings 3D is a free subdivision modeler inspired by Nendo and Mirai from Izware.
MisfitModel3d: Windows, Mac, *nix; open source. Easy to to use, can do modeling, texturing, frame and skeletal animation. Free and under active developpement.
Tiger Viewer (formerly OgreModelConfigurator) - open source. A tool to view and configure Ogre mesh, animations, particle, sound and event.
Ogre Meshy (formerly wxOgreMeshViewer) - open source. A viewer for Ogre meshe files. Support of animation time manipulation.
CEGUI Mesh Viewer - open source. Viewer for Ogre mesh files, including detail display, optimizations, animation playback.
Show Mesh - open source. Viewer for Ogre mesh files. Outdated.

Animation

CharacterFX Freeware, since 2008. Create animation easily, with weighted Bones, and supports many formats, using lua script for import and export.
FragMotion Shareware. Create animation easily, with weighted Bones, and supports many formats.
Tools: Blender: Windows, Mac, *nix; free under GPL. Animate a model both with shape morphing, and/or weighted bones (skeletal animation).

Physics modeling

Scythe Physics Editor A open-source physics editor compatible with a variety of physics engines. Includes native support for Ogre.

Drawing and painting

Drawing/painting tools are used to create textures for models and landscapes. Textures are simply bitmap images that are stretched over polygon meshes to make them look realistic.

Spacescape : Windows, free, MIT license Create seamless space skybox textures.
BodyPaint: Windows, Mac; Commercial. 3D paint software, allows direct painting on 3D models.
Displacement Map Creator : A tool to make displacement maps from normal maps (win32). On same site, check how to make Normal Map from any Real Subject using a camera, a flash light and a computer : How to make normal maps from real surfaces.
Genetica : Windows only, commercial. A professional-level seamless texture editor. Has an innovate node-based interface and comes with more than 500 finished texture presets.
GIMP normalmap plugin : Windows, *NIX, free A plugin to The GIMP which allows for easy creation of normal maps from heightmaps.
GimpShop: Windows, Mac, *nix; Free under GPL. A Photoshop look alike hack for the Gimps ui currently in Beta release. Makes it easier for us photoshop users to move across. Gimpshop is now very out of date, and the publisher's home site is now offline.
Microsoft Paint: Windows only; Commercial, but bundled with Windows. Sometimes simplest is best. And you can't get much simpler than MS Paint.
Nvidia -Texture Tools : Windows, free Several texture tools, not bound to NVIDIA cards only. Amongst them a tool for generating normal maps from heightmaps.
Paint.NET: Windows 2k/XP; Free under BSD-like license. Less powerful, but much easier to use than GIMP, this program offers Layers, Filters and a Plug-in interface. Gui resembles Photoshop.
Paint Shop Pro: Windows only; commercial. For some, the best image manipulation software, even better than Photoshop. Now owned by Corel.
Photoshop: Windows, Mac; Commercial. Photoshop is the premiere product used by professionals. Photoshop Elements is a stripped down version for less money.
TATTOO: Windows, free freehand tool which allow you to paint your uvmaps in 3D, as bodypaint3d, but free.
The GIMP: Windows, Mac, *nix; Free under GPL. The GIMP is a fully-featured image manipulation program. Version 2 included a significant UI overhaul which made the tool much easier to use.
Texture Maker: Windows; Shareware Very powerful tool to make seamless textures and bump maps. Shareware can only save textures up to 320x320 pixels. Great if you only need to make textures and don't plan on using it for anything else.
Wood Workshop : Windows only, free. Creates everything from wood floors to tree bark. Likely the best seamless wood texture generator out there.
Seamless -Texture Generator : Windows only; commercial. tool for creating professional seamlessly-tileable textures from photographs quickly and easily.
Texture Studio : Windows only; Freeware. -Texture Studio is all you need to produce professional quality textures for use in games and tiled backgrounds.
MaPZone : Freeware. Very powerful procedural texture generation tool. Outputs many types of maps (diffuse, normal, specular, etc). Free for personal and commercial use.
Crazybump : Freeware as Beta. Normal map tweaking-editing creation tool.
Xnormal : Freeware. Specular/Normal/occlusion/relief/height map tweaking-editing creation tool
Tools: Blender: Windows, Mac, *nix; free under GPL. Texture and vertex painting directly on the 3d model; baking of textures, ambient occlusion, tangent space normal maps, etc...

World design

Worlds normally consist of exterior terrain populated with entities (trees, houses, monsters, etc.), water, sky and light sources. Very broadly speaking, there are two problems in creating worlds: creating the terrain, and populating the terrain with all those other things (entities, water, sky, light sources.) World design tools help to solve these problems. Some tools deal exclusively with terrain generation, while others help with laying out the scene.

Terrain generation

Terragen: Windows, Mac; Free for non-commercial use until v1.0 released. Permits development of gorgeous terrains. Terrains can be read in using the Terrain Scene Manager.
Leveller: Windows; Commercial. Heightfield modeler with a simple interface and a number of useful plug-ins. At time of writing, $99 for a license. Free demo available.
HME: Windows, Linux; Donationware. Simple heightmap editor with a paint-like interface.
Freeworld3D: Windows, (Linux in development); Commercial ($20). A terrain editor, with heightmap editing tools (raise, lower, smooth, flatten), support for painting texture layers (compatible with texture-splatting techniques used in PagingLandscapeManager and applicable to default Ogre Terrain), generating shadows, placing meshes and custom entities, skyboxes, and more.
Advanced Landscape Editor (ALE): Windows; Commercial ($39.99). A realy nice and easy to use terrain editor. It has a WYSIWYG interface and makes terrain editting a breeze. Very useful for creating height- and lightmaps.
Kashmir3D: Windows; Free. This terrain generator is quite old (last update in 2004).
Large 3D Terrain (L3DT): Windows; Free, Commercial. Very capable terrain generator that generates Heightmaps, Texturemaps, Lightmaps, Normalsmaps, Textures. Maximal Terrainsize is 131,072 by 131,072 that can be saved as a pack of smaller tiles. Free version has reduced capabilities (smaller resolutions (max. 2048 by 2048), single-processor rendering, etc.) but no restrictions on use.
3D Studio Max Heightmaps: Tutorial. Use a 3D Program to create your heightmap. You will need a 3D Program that support muilti UV set and Render to texture function. 3DSMax and Maya include these function.
PnP TerrainCreator: Windows; Free, Commercial. Modern heightmap based editor for interactive and automated terrain generation. Allows import of Ogre meshes. Scene export. Tree-placement and grass coverage. Tutorial: Ogre3D export with splatting shader
EarthSculptor: Windows; Commercial. Intuitive realtime heightmap editor, with good texture painting and sculpting tools. Exports heightmap, normalmap, and lightmap separately. Would be perfect if it exported ogre materials.
Editable Terrain Manager: modify with Ogre itself.
Artifex Terra: Windows; Free Beta. Intuitive WYSIWYG heightmap editor & painter based on the Editable Terrain Manager. Features: artpad support, brush-system, texture painting/editing, colour painting, sculpting tools, terrain and colour filters, ogre object placement and editing. Exports heightmap, colourmap, lightmap and coveragemaps separately.
Terrain Generator: Windows, Freeware. Terrain Generator is an intuitive and flexible terrain generator, which allows users a 3D control over the map (as opposed to a painting style 2D editor). While capable of exporting heightmaps, it is unclear as to whether the textures can be exported alongside the heightmap. However, it can export to a number of other formats including .vmf, .map, .rmf, .t3d, .obj and some others, so exporting textures may be possible by means of exporting through a different program.
MojoWorld 3Windows, Commercial+Demo Create worlds , sculpt, and populate them. MojoWorld's procedural fractal engine creates pixel-level detail at any resolution, distance or field of view.
TerraNoiseWindows, Free Procedual fractal generation based on libnoise.
Tools: Blender: Windows, Mac, *nix; free under GPL. Can generate height maps, shadow maps (baking), and texture maps (baking). You can use custom-made or procedural textures on a grid, or use the ANT Landscape plugin.

Full world design

Using exporters available for the following programs allows for export to a scene format known as DotScene. This can be efficiently optimized using the DotSceneOctree scene manager, and lends itself well to large outdoor areas.

3ds Max: Windows only; commercial. Among survey respondents, 3ds Max was the unanimous choice of commercial tool for object modeling with Ogre. The Yake Octopus exporter allows for easy DotScene export.
Tools: Blender: Windows, Mac, *nix; free under GPL. Blender is an open source modeling tool, with many advanced features and a very active and dedicated community. The GUI need getting used to, but lends itself to a very efficient work style once learned. A scene exporter and other tools are available for designing in blender.
Maya: Windows, Mac, *nix; commercial. The LFA Scene Manager exporter allows for easy DotScene export.
EGO Game Editor: open source. For outdoor map creation. Support of terrain, light, sound, fog, animation, Hydrax (water), Caelum (sky), etc.
Ogitor: open source. Scene builder with terrain support.
OGRE Studio: open source. Suite of tools customizable via plug-ins (material editor, mesh viewer, scene editor, etc). Project closed in 2007. (source still available)
GameDirector (aka RealityEditor): open source (look also to the project forum)
Glue Editor - Real-time scene editor with a simple user interface designed specifically for Ogre projects

Level design

The term level is normally used to describe the interiors of building, dungeons or industrial complexes in which many games take place. Levels are different from exteriors in that they typically consist of regular geometry (hallways, staircases, etc.) rather than terrain. Level design tools typically allow the definition of the level's geometry as well as the placement of entities (furniture, monsters, etc.) and light sources.

While levels can be displayed in any scene manager, Ogre provides the BSP scene manager which employs BSP culling and collision management to render levels efficiently. This scene manager is no longer subject to legal restrictions since the release of GTKRadiant and q3map2 under the GNU GPL by id Software. BSP levels are generated from Quake .map files, created via a map editor.

3ds Max: Windows only; commercial. For those who can afford it, 3ds Max can be used to edit levels. The Octopus plugin can be used to make 3ds Max more Ogre-friendly. Exported levels are rendered at runtime with the DotScene scene manager.
Blender: Windows, Mac, *nix; free under GPL. Blender is a free modeling tool, with many advanced features and a very active and dedicated community. The GUI need getting used to, but lends itself to a very efficient work style once learned. A scene exporter is available as addon project.
GtkRadiant: Windows, Linux, MacOS X; free under the GNU GPL. The level data can be created with this editor and must be compiled with a BSP compiler (such as q3map2) to be used by the BSP scene manager. The q3map2 BSP compiler does support lightmaps generation.
Maya: Windows, Mac, *nix; commercial. For those who can afford it, Maya can be used to edit levels. The LFA Scene Manager MEL scripts can be used to make Maya more Ogre-friendly. Exported levels are rendered at runtime with the DotScene scene manager.
Quake Army Knife (QuArK): Windows; GPL License. QuArK is another Quake 3-format level editor. Levels are generated in .map format, which must be compiled to BSP for use in the BSP scene manager.
Worldcraft/Hammer: Windows; Only to develop new levels for Half-Life and other compatible Valve products. Hammer (called WorldCraft prior to 3.0) was developed as a modding tool for the Quake and Half-Life games. Licensing of Hammer prevents its general use, though I believe the restrictions on earlier versions were weaker (unable to find references at the moment, though I believe WorldCraft was purchased by Valve and renamed to Hammer). WorldCraft generates MAP models which must be compiled to BSP form for use in the BSP scene manager.
DeleD is a 3D modeler leaned toward interior level creation. It has a free Lite version and a low cost Pro version. Easy to get the hang of and has a free Ogre exporter plugin that works well.

Shader Tools

HLSL2GLSL: Windows, Mac OS X; BSD License. Library and tool that converts HLSL shaders to GLSL.
FxComposer: NVIDIA's shader development tool.
Render Monkey: ATI's shader development tool.
QShaderEdit: QShaderEdit is a simple multiplatform shader editor inspired by Apple’s OpenGL Shader Builder.
Mental Mill : GUI driven shader development (well integrated with NVIDIA's FXComposer2)

Other tools

Giles: Freeware Gile[s] is a Global Illumination Editor. It allows you to create a radiosity lightmap for a scene. A lightmap is another texture layer, that adds light and/or shadow to the underlying texture. The radiosity lighting technique is far superior compared to any real-time technique. A Gile[s] plugin that allows exporting Ogre meshes and materials (contributed by Walaber) is available as source in the ogreaddons and as a binary distribution on his homepage.
Particle Universe plugin: Commercial ($10). Engine for particles in Ogre. Contains an SDK with editor, API description, Manual.
Particle Accelerator: Open source. Tool for creating particle systems by a GUI.
OGRE Particle Editor: Open source. Visual particle system editor.
ParticleFX plugin: Open source??. A particle system add-on.
Ogre Particle Lab: Free

Table of contents:

2D Graphics

So You Want To Be a Pixel Artist?: An excellent guide to basic 2D tile-drawing and animation.

Concept art wiki: An excellent wiki for concept artists.

Blender

Interior Modeling: Scroll down the page to Blender Modeling section ;)

Modelling

Low Poly Tricks, Tips & Techniques: Some helpful information about low-polygon modelling.
Low-poly Modelling: Links to tutorials about low-poly modelling. The one above is one of them.

Tutorial Links

GameDev.net Tutorial List: A helpful list of tutorials for various programs and general-purpose modelling
TutorialesPM Spanish Ogre Tutorials: Here you can find some Ogre tutorials for spanish people.

LIGHT - a detailed tutorial: This is not 2D or 3D material, but anyone wishing to create an illusion of reality should have a good understanding of how light behaves in the physical world.