The Planet Hunters! I gave the website a try and like Zooniverse's other projects it is very, very easy to get up and running. The interface shows you a light curve of a star from Kepler, and you are asked to look for dips in the star's spectrum, drawing a box around them. (I asked how tight the box is supposed to be, and the answer is that it is supposed to just be drawn around the part of the spectrum that contains the dip, so it's best to zoom in to get detail on the light curve). Go give it a try!