In general, if you want lots of processing power, the pc104 board is a great, small, standard system that can be of great use to robot designers. For those who have not come across them before, pc104 boards are complete pcs on a small (about 4 by 4 inches) board - including cpu, memory, disk-on-chip (for storage), parallel ports, serial ports, usb, vga, lcd controller, sound, pcmcia and a host of other options (depends on the board). Some of these can have current draws of under 1Amp. Furthermore, because they are standard pcs, they can run standard linux (or windows, if you wish...). Many also have ide so you could hook up a hard drive or cd drive if you really wanted to.

Just to be even more flexible, the boards stack using a standardised socket (based on ISA) and there are hundreds of different cards - from gps to video capture cards.