well a 24V motor wont work, cause putting 24V on a robot is a pain (a lot of battery weight)
the 6V one is ok, but somewhat weak (cNm is centi-newton meters, or newton meters divided by 100). the 18º step is poor resolution though, meaning it will work but be jerky.
one day ill write a good stepper motor tutorial
, but the place holder page will sorta explain how they work . . .
the motors from electric screwdrivers and windshield wipers will work fine, but may draw a lot of power so you may have problems finding a motor driver. windsheild wiper motors run aroun 12-13.5V, and draw like 4A of current. your best bet will be the screwdriver motor.
floppy drives and vcrs, although they get power from AC mains, convert the power to DC to run. they probably wont be geared motors, and will be weak, so not very useful.
i would say hook up two powered screwdrivers by hacking the power wires to your bot.