Following/Followers
Get flash to fully experience Pearltrees
The different lists of active vs. inactive tweeters, people not following back, etc. are REALLY helpful. I can see this being a great tool for my clients as well. @emichaud - February 2011
ManageFlitter
Tweexchange
Tweexchange » Search for available Twitter usernames and Domain Names at the same time by Jul 7
MapFollowers