http://www.linuxmint.com/oldreleases.php
MATE was originally a fork of the Gnome 2 desktop that was added onto and improved after the Gnome team abandoned it for Gnome 3. Many of Linux mainstays work out of the box with MATE such as Compiz, for example.
Cinnamon was a rework of Gnome 3. Many people hate the Gnome 3 environment but the underlying technology of the environment is sound. So, the Mint team went to work to create an environment based on Gnome 3 that would bring back the more familiar desktop environment that many people prefer. Thus, Cinnamon was born.