The Best Thing project
The Fairest Thing project
The Funniest Thing project
TheCutest.info, TheFairest.info, and TheFunniest.info are a trio of side projects to the webcomic xkcd. They host contests where people vote to select the best choice from a large pool of user-submitted options. Instead of the usual voting methods where people rank things or vote things up or down, we let people choose which of two things is better. Then every few minutes the server does some analysis (for how this works, click here) and comes up with a list of the best things. It's a good system, and is free of a lot of problems other web-voting systems have, like a bias toward older items.
Note: All these images are user-submitted, and most have been floating around newsgroups and such for years. If one of these is from your site and you want it down just email firstname.lastname@example.org. If you're offended by something you've seen here, I'm sorry. The algorithm moderates things pretty well, but browsing random images submitted by users on the internet carries the inherent risk of seeing something you'd rather not. If you don't like an image, just vote for the other one. It'll probably get weeded out fairly quickly.