Uboot:
Official website: http://www.denx.de/wiki/U-Boot
Download address: http://www.icdev.com.cn/batch.viewlink.php?itemid=1694
STLinux:
Official website: www.stlinux.com
Download address: ftp://stlinux.com/pub/
linux:
Official website: http://www.linux.org/
Download address: http://www.linuxhq.com/kernel/v2.6/index.html
yaffs2 official source code download address: