I think I have settled on a microcontroller for this first project... a Microchip PIC 16F877. With plenty of I/O and Risc processing, it should be adequate. Also settled on my on-board power supply. I think I will have 12v at 2 amp hours. This isn't a very large robot, so I think it should run for a couple hours with that, but even so, I have plenty of room to triple that.