The Sloan Digital Sky Survey (SDSS) is recording images of a large portion of the sky that will eventually encompass a million galaxies. With such a large number of galaxies, astronomers can finally begin to understand how they form and evolve by comparing various populations to each other with large enough numbers to draw real conclusions about their origin.
The problem? Each of these galaxies needs to be identified as either a sprial or an eliptical galaxy, in order to derive the relationships which the survey seeks. And there are some jobs that computers just aren't up to yet. Or at least, getting a computer to perform them requires ridiculous amounts of processing power. Among these is the determination of whether a galaxy is spiral or not, and whether a spiral galaxy appears to be rotating clockwise or counter-clockwise.
So, they're asking for our help. Sign up at Galaxy Zoo, run through the training images, take a short (15 question) test to prove that you've been paying attention, and start digging into the images. Some of them are amazing. I snagged the pic for this post from one that I was asked to categorize. I'm sure the best are still ahead. And don't worry that you'll make a mistake and screw up the project. Each of these images is reviewed multiple times in order to determine its type. If you screw up, others should catch the mistake. Give it a look!