ilo - Premium Twitter analytics
BlockParty - Real-time voice chat rooms from the creators of turntable.fm
Accountanalysis - A tool to evaluate Twitter accounts
Red Block - Red Block is a browser extension that lows you to block users from your Twitter account.
Tweetastic - Better Twitter analytics, scheduling and more
Secateur - Use Secateur if you want to temporarily or permanently block or mute (or both block and mute) a Twitter account and all its followers.