Adblock Plus - AdBlock Plus is a browser extension for Firefox, Chrome, Opera, and several other popular browsers that prevents intrusive ads like pop-ups and malicious code from appearing on websites you visit.
ilo - Premium Twitter analytics
BlockParty - Real-time voice chat rooms from the creators of turntable.fm
Accountanalysis - A tool to evaluate Twitter accounts
Twitter One Click Block - Add a block button for a simple one click blocking.
Seekmetrics - Instagram, Facebook and Twitter Analytics.