Hot or Not for Twitter! You can link your Twitter account to your TwitPic account so people can see other pictures of you in addition to your avatar. Browse boys, girls, or everyone - and follow the people you think are hot.
Sure, it's a little shallow - but it's incredibly well designed. Very easy to browse through people, and it really is addictive to get hot votes for yourself - check me out at http://hottweeters.com/sachinag.