TweeterTags is a Twitter application, currently in public beta, which aims to add to the existing functionality of Twitter by allowing users to tag themselves, and find others according to similar tags. Tweeter Tags makes it easy to declare your interests and find new, like-minded friends. Have a question you need answering? Find relevant people on Twitter to ask.
TweeterTags works in two ways. Firstly, it allows you to tag yourself according to your own interests, skills or topics; Secondly, it utilizes information via the Twitter API to show you what tags your friends are using and allow you to connect with them and others sharing the tags you're interested in.
It only takes a moment to sign up and tag yourself (I already did), and if you use PowerShell then check out Jeffrey’s Get-TweeterTag script.