Step 2: Get motors
Right now I'm going for quick and dirty.
So, HarborFreight.com here I come!
I bought a bunch of cordless drills from Harbor Freight for about 15$ each. They come with the motor (of course), 18V battery, and charger. That is a pretty good price for all that. Also I like the way you can just jam stuff in the drill chuck and tighten it down. Nothing easier than that for attaching an axle, drive-screw, or whatever.
The problem with these motors, is that with coil resistance of only 0.5ohm and a 18V power supply, we are dealing with alot of power. (some math: V = IR... so I = V/R or I = 18/.5 which is 36Amps) ( more math: W = VI (right?) or W = 36 * 18 which is 648 Watts (is that right?) if that is correct, then running these at full power uses as much power a 6-and-a-half 100 watt light bulbs (really?))
If you are used to regular Arduino type stuff, then this kind of power will, as they say, burn up your sh*t. (even if my math is wrong - 648 watts? yikes)
But let's deal with that latter and play with the boxes!