Kensington and iGo both make universal power supplies that can be used to power various devices using special tips to configure voltage and current settings. I've often wondered if these could be hacked to use as lab supplies. A recent find of a Kensington 70 watt supply led me to do some experimenting.
I'm happy to report that both of these power supplies can be used as low-cost bench power supplies with adjustable voltage and current limiting. The Kensington types in particular are great building blocks for simple knob(pot)-controlled to more featured microprocessor-controlled supplies.
Kensington supplies provide 0 - 25 volt outputs at up to 6 amps. Voltage and current are each controlled by a pair of resistors in a voltage divider arrangement. A digital pot or DAC output can easily control these supplies.
iGo makes two types of supplies - a laptop supply and an "accessory" supply. The second is what I experimented with. It's more limited with a 3.1 - 9 volt range at up to 1.5 amps. Voltage and current are each controlled with a single resistor.
The details can be seen here:
Kensington SuppliesiGo SuppliesEither type of supply can be bought new for $15 or less. Add a few parts and you can have a nice bench supply.