Flock - A faster way for your team to communicate
Listr - Listr lets you explore some of the best lists on Twitter, curated across your favorite categories.
SocialRank - Graph search for TWTR. Filter by interests, location, etc
Refined Twitter - A browser extension that improves the Twitter experience
Accountanalysis - A tool to evaluate Twitter accounts
Vicariously.io - Create Twitter lists based on the follows of other users