Rick's Third Party Firmware Webpage

I have Buffalo Technology's WZR-600DHP router, running dd-wrt. (Buffalo support forums; firmware downloads)
I use Tomato firmware on my Linksys routers. FAQ. (Support forums)
dd-wrt firmware runs on many different routers. I have it on a couple of $15 routers from Frys! Support forums. Wiki with tutorials, FAQ, Scripting, etc.
The MyBook World Edition can be hacked to have its firmware updated to support tools like ssh, etc. (Support forums)
You can use CHDK to upgrade the firmware in your Canon Powershot camera. (Support forums)