I'd like to build a basic two-wheeled robot (two wheels and a support skid)... anyone know of any inexpensive simple motors to start out with (ideally ones that can be powered both directions)?

hi ranger,

at my local robotics club they are building a bunch of "bugbots", basically just a pair of electromotors rigged to a metal plate with two antenna-like sensors on the front which reverse the polarity on the motors when they hit against something. They have motors by the bag. I'll ask this Tuesday where they got 'em and get back to you if nobody chimes in in the meantime.

Thanks! Ideally I'd like to make something like that, except with a slightly more advanced logic (like backup, turn, continue forward instead of just switching polarity)... so pretty much build some basic hardware and spend months fooling with the programming.

Meh, I wish there was a robotics club in my area; there's a F.I.R.S.T. team, but 7 meetings a week for 6 weeks doesn't work with my schedule, and this is the last year I would've been eligible for.

Check out http://www.Pololu.com. they have a number of different kinds of motors and motor controllers that will allow variable speed in both directions.