Hi all. My friends and I are building a robot powered by a libretto laptop running Linux (connected to an arduino for motor/server control). I would like to experiment with robot vision and AI, so I'm looking for a USB web cam (it doesn't have to be fancy) with the following requirements:

-It's cheap (under $50 preferred, but this is flexible)
-Easily usable on a Linux system
-Has an C API so I can grab image data off of it for processing (without this is would be very useless).

I figure that there are similar projects out there so I'm hoping maybe someone can point out a model of camera that has these things. This is my first time doing anything like this so I'm not looking for anything with fantastic image quality, just something I can play around with.

Thanks for your time
-Alex