Find Twitter Users that You Share in Common With Others

Who Follows Whom is a simple Twitter tool that allows you to discover the Twitter users that are followed by or following specific users. By entering several usernames (at least two) in the tool, you will be able to find out who they are following in common and who follows them as well.

This might be a good way to find out more new users to follow because if these people are followed by users you like or if they are following the users you follow, there might be some common ground in terms of interest.