How about a benchtop power supply from an old computer power supply.
I know that Ben did something similar with an old computer power supply in one the episodes, Episode 40: See Ben's Energy-saving Universal Wall Wart Episode.
I'm thinking more of a supply that besides the 3.3V, 5V, 12V fixed supplies and the USB charging uses a variable switching supply and a potentiometer to supply 0-12V.
A built in volt meter would be nice so you can see your variable output voltage, maybe a shunt to measure apmerage as well.
Maybe a fixed 9V supply for your favorite micro controller dev board or boosting the 12V to supply more than 12V on the variable output.
So take the "Universal Wall Wart" and upgrade it to a variable benchtop supply with volt meter and maybe even Amp meter...
