Homemade input devices?

Has anyone ever tried making, or know a site about making, homemade input devices? Or even customization and modifications on existing homemade devices?

I like to tinker around and build things, but for whatever reason I've never gotten into the whole computer hardware thing, despite my love of using a computer. So I was looking to see what I would need for something like that. Are there any cheap kits or devices that I could use or take apart, and what sort of software or hardware would be needed to customize a keymapping?

X-keys has their "matrix" board. You might want to explore that route.

This is what somebody did with something similar:

http://www.dual-boxing.com/forums2/viewtopic.php?t=1474

That is totally awesome. I'll have to check that out.