I just found this, which looks interesting. This is a fairly small (4" x 4") Linux based controller. This should be small enough for most robots. The price is a bit high for what I want to spend, but this might be workable at some point.
8-Dale
That does look nice. I like the two USB ports(think webcam). The price is a little high but for a single board computer it is not bad.
The OmniFlash single-board micro-controller comes preloaded with theLinux operating system and all the utilities you need to start development. Our low-cost development kit contains a bootable development CD, eliminating the hassles of getting a cross compiling environment set up.The controller features 16MB of Flash Memory and 32MB of SDRAM.