We use Basic STAMP's all day here at work to run our test equipment. Super-easy to program (which is likely why we use them), but SLOW, inefficient code, and retardedly expensive. I've blown at least 6 of the $90 BS2P40's in the last few months. They don't like static charges. I'm changing to Cypress PSOC chips (they have tons of configurable devices embedded on the chips) since we use those in products we sell and so guys here know how to program them in C, but I use Atmel parts exclusively at home. I'd reccomend Atmel or PIC any day over Basic STAMPs, unless speed or cost doesn't matter and you need to have kids program it.
I've got the SurplusCenter control boards mentioned above (both the old plain aluminum one and the black anodized one) but haven't done much beyond spinning a motor with them. Hopefully they're easy enough to interface with.

Lately I've been machining at 10k RPM / 120inches / minute and feel the need for more speed though. I like the idea of a nice high speed spindle with the RC motor attached. I could go for 20k RPM as long as it doesn't sound like a screaming Banshee. (Dremel tool.)

It's fun watching a rooster tail of aluminum spit out of the cutter!