For Finding People

• Following who the Follower is Following: One of the best ways to find people with similar interests on Twitter is to see who someone you know is already following on Twitter and then follow them too. Find your favorite website, magazine, or search by someone’s name using the “Find People” feature after you login to you Twitter account.
• Twellow & Wefollow are the people finders of Twitter, kind of like the Yellow Pages are for businesses.
• Twitter’s “Who to Follow”: On the right sidebar, Twitter will suggest people you might like to follow.
• BlastFollow: Automatically follow anyone who tweets under a certain hashtag in one quick blast.

For Listening

• Tweetdeck: The two advantages of this client are language translation and auto complete Twitter usernames.
• Hootsuite (with Fluid for Mac): Hootsuite is an online tool but can be transformed in to a desktop type application with Fluid for Mac. A nice interface but it currently lacks the two features above from Tweetdeck.
• Big Ear with Yahoo! Pipes: To follow mentions about your brand or Twitter handle, grab RSS feeds from Twitter Search and Social Mention and combine into one single feed using Yahoo! Pipes.

For Searching

• Twitter’s Advanced Search
• Google Search – Updates

For Backup or Exporting Tweets

Tweetake: Backup your personal tweets.
TwapperKeeper: Export Tweets including hashtag tweets to spreadsheet.

For Sales

Twitter’s Advanced Search by hashtag, area, keyword, and/or location.

Twitcatch: Find people by hashtag, keyword, or location and then follow-up with a tweet in a couple of clicks. The service is still in beta. (