GogoBoard - easy to construct open hardware platform (about $40 to build)

[iamwil]

http://www.gogoboard.org/cocoon/gogosite/home.xsp?lang=en

[kqr2]

A similar low cost open source hardware platform that appears to have traction is the arduino:

http://www.arduino.cc/

[jwilliams]

You program it in Logo no less.

[iamwil → jwilliams]

Actually, the reason why I put it on here was because you can use it with Netlogo, so you can do real life simulations of large number of robots.