So yesterday, after months (years?) of occasionally looking at a partial pile of parts, I finally completed one of my many lesser brewing projects--I now have a stir-plate, for yeast starters and propagation and the like. I'd put together the computer fan and magnet before, but couldn't get a dimmer switch to adjust the speed, and was having difficulty imagining how I'd support the whole thing. Enter the various online forums I habituate, and the thread here. A nice, step-by-step tutorial, complete with photos.
I already had a fan and a project box (fan from an old computer that's slowly being cannibalized for parts, project box that was going to be for the HERMs controller). The HERMs controller (which is complete--just waiting to amass parts for the final build) is going to be powered by a 9V DC adapter (wall wart); I simply got a matching jack for its plug to use in the stir plate. Purchased a rheostat/potentiometer, a knob for it, an on/off switch, and some magnets, and assembled as per the instructions. (Pictures will be forthcoming soon, if I get around to it...)
Add one stir-bar from the LHBS (Maryland Homebrew), and after a little practice, it works fine! Woohoo!