Tweetizen

Tweetizen is a site that lets you create groups of people or groups by topic that you are interesting in paying close attention. You can customize the name and look and feel of your group to make it fun as well. They have a very easy how-to section.

To start you need to grant access to your Twitter account by filling in your user name and password and then you are all set to segment the people your are following, or the topics you are interested in to your heart's desire!