From the folk who bought you the citizen-participation astronomy projects Galaxy Zoo, Moon Zoo and the Milky Way project comes Planet Hunters. You can help find extrasolar planets for the Kepler Space telescope team.
At planet hunters you scan star-intensity traces from the Kepler Space Telescope looking for the characteristic dips in a stars intensity caused by a planet transiting in front of of the star.
The Kepler folks have computer programs to do this, but people tend to be better at finding the patterns of transits than computers. So this is you chance to aid sicence, and mybe find another world out there. I'm enrolled, but so far I've only found variable stars (see image above). You will need a fair bit of patience as your sort through the traces.
But still, finding another world! Imagine that!
(Tip of the hat to the Bad Astronomer)