Getting ready to put together another electronics class. This one will be themed around robots, so I'm looking for likely candidates.
Here's Popular Mechanic's Build Your First Robot project. Points to more details here. They're estimating about $100, but I think it can be pulled off for less.
And via Hackaday, the Red Rover. It's tiny, 3D-printed, and uses rubber bracelets for treads. May be a pretty cheap way to go!
I've got parts coming in for both, so I'll make a page for each of these and put collected information there.