Controlling Robots with Linux?

propain asks: "I've recently heard of a few robots controlled with Pentium processors run by the Linux kernel. I would love to build a robot with Linux-for-brains and write my control code in C. What are the various challenges one must undertake in receiving input from various sensors and sending certain electrical voltage and current pulses to actuators and other output devices? I assume the answer lies in device driver programming and embedded Linux systems?" Anyone have pointers to webpages with useful information on this subject?