REAL-TIME THEMATIC TRENDS TRACKING

• http://twendz.waggeneredstrom.com/
  
• http://www.twitscoop.com/
• http://www.retweetradar.com/
• http://spy.appspot.com/
  
• http://microplaza.com/public
  
• http://twistori.com/ (see screenshot above -> translate tweets into : love, hate, think, beleive, feel wish)
  
• http://www.peoplebrowsr.com/ (kind of super online tweetdeck - still in alpha)
  
• http://twitterfall.com/
• http://www.qapture.net/ (aptures and ranks the links being shared right now by some of the most interesting folks on Twitter)

DATA VISUALIZATION

• http://yvoschaap.com/twitterthoughts/ (Flash chart)
• http://www.neoformix.com/Projects/TwitterStreamGraphs/view.php
  

GEOLOCALISATION

• http://twittervision.com/ (Google Maps)
• http://www.trackthisnow.com/twitter/ (Google Maps)

TWITTER PRODUCTIVTY TOOLS

• http://tweetstacker.com/ (simple twitter client that shows users and messages in a threaded display instead of every tweet from every person)
• http://twitpwr.com/ (tracks the number of clicks that you drive via the Twitter API, and give your account a Power Rating)
• http://twitpic.com/ (lets you share photos on Twitter)
• http://www.twaitter.com/
  

DIRECTORIES

• http://wefollow.com/

SOCIAL INFLUENCE

• http://twinfluence.com/
• http://twitter.grader.com/
• http://klout.com/
• http://twittercounter.com/

TAGS

• http://hashtags.org/
• http://tagal.us/

SERVICES USING TWITTER

• http://www.breakingtweets.com/

added later

• http://www.twibes.com/
  
• http://tweetstats.com/
• http://socialtoo.com/
• http://hootsuite.com/
• http://twitturly.com/
• http://retweetist.com/
• http://favrd.textism.com/
• http://twitlinks.com/
• http://tweetmeme.com/
• http://twist.flaptor.com/
• http://silentlycrashing.net/tweetpad/
• http://plodt.com/
• http://twitter-friends.com/
• http://www.socialwhois.com/
• http://www.tweetizen.com/
• http://tweetscan.com/
• http://tweetchannel.com/
• http://monitter.com/
• http://tweetzi.com/
• http://twemes.com/