[EricH]

We'll start with the easy stuff.

Continuous-rotation servos: Servos are motors that will go to a given position and do their best to stay there. However, some folks make continuous-rotation versions, which look the same but rotate continuously.

Go with a regular triangle; the mechanical work will probably be easier. Also, look in CD-Media for some pictures of kiwi drives.

VEX motors: The VEX website is http://www.vexrobotics.com/; motors are under the "motion" category. Also note the omniwheels and other miscellaneous items...

Edit: Yep, those or their cousins in the same line.