|Updated 5th March 2013 with an extra photo – thanks PiBorg!
Here’s a new board from PiBorg. It can turn on and off 4 devices including fans, motors solenoids and relays etc from the Raspberry Pi.
It comes in two flavours: a £5.99 basic model (top) and a £9.99 ‘with pre-soldered wires’ (bottom)
The website itself contains various pieces of information and a Getting Started guide. What would be nice is some kind of shopping list for which fans, motors, etc would work, but there are some voltage and amperage guides, so you should be able to work it out. I expect they are easily contactable too.
For that kind of money, it’s worth a gamble.