Toradex provides Linux support for all other than the PXA module family in house.
For information about building U-Boot and Linux kernel from source code have a look here.
Check the Colibri Recovery Mode to learn how to program Linux on to a Colibri T20.
Furthermore there are open source projects from 3rd parties which provide support for the Colibri modules.
Please let us know if your Linux community site is missing in this list.
You can use Colibri Loader or the WinCE default Bootloader Eboot to download Linux Uboot to the Colibri module.
First you have to create a compatible binary using the CreateTBin tool.
After that you can download the binary with Colibri Loader or Eboot.
Eboot, our default Windows CE bootloader, is also capable of running Linux. Please go to Eboot for more info.