We use a simple cart, made of aluminum and casters. Very simple, very nice.
To pimp it out a bit, I always like:
- removable handles (so you can work on robot on the cart)
- Storage for batteries and a few other necessary items
- A turn table so you can pivot the robot while working on it
We like the ol' KISS principal on our robot, and the cart is no different. Cheap, Easy, Reliable, Simple, Quick - everything you need.
(But ground effect lighting, mass storage, stereos, cray supercomputers, and hovercarts are all really cool too!)