For the more serious hardware hacker, no tool is more essential than a variable power supply. Able to supply voltages and currents adjustable to the tenths of a unit, the supply will run just about any reasonably-powered electronic device including circuits, iPods, laptops, and more. In only the last few weeks I’ve used my own to test a portable DVD player which had no wall adapter, power an iPod attached to a breakout board, and temporarily resurrect a dying PowerBook. I bring all this all up because I happened to see an influx of these great tools available on eBay using one of my saved searches, and thought others may benefit from them. To find them, search eBay for (HY30*,HY50*) supply or click here.