DIY Power Supply
Retail an adjustable power supply like this would go for ~$50. You can make one for ~$10. If you salvage parts from stuff destined for the trash, you can make one for free-ish.
Everything with a red arrow pointed at it was salvaged from old hardware, mostly an old TV set.
This is how you recycle.
The power supply uses the LM317 voltage regulator. The input voltage can be anything from 9v to 30v. The output is adjustable from 1.25v to within a few volts of the input voltage. A good guide to follow for making your own can be found here: http://www.ladyada.net/library/equipt/diypsupp.html