I am building an ASP.NET web site where the users may upload photos of themselves. There could be thousands of photos uploaded every day. One thing my boss has asked a few time
CrowdSifter by Dolores Labs might do the trick for you. I read their blog all the time as they seem to love statistics and crowdsourcing and like to talk about it. They use amazon's mechanical turk for a lot of their processing and know how to process the results to get the right answers out of things. Check out their blog at the very least to see some cool statistical experiments.