Tweet Boards - reminds me of Crowdstatus and Gridgit. Display widgets on one page for a bunch of Twitter users, similar is TweetPeek, but that's more a stream. Here's an example.
Twitscoop - a what's hot tag cloud based on word frequency and graphs posting frequency, some of the Twitter search engines do this sort of thing
My Tweet Map - Displays a list of the latest tweets of people you follow on a map. Your stream is on the sidebar, just click on a tweet and it will take you to that users location. Most of the other Twitter map services are on auto-pilot, I liked the simplicity of this one. You can reply to tweets and post a new tweet.
Tweet Later - this service does a few things: a Twitter reminder, auto-responder tweets to new followers and an auto greeting tweet, and schedule 12 auto-tweets an hour...for more auto tweets see TweetResponse, TweetAhead, AutoTwit, and for more reminders see ReTweetMe and Twitter Timer.
Tweeqs - Twitter cliques...apparently I'm in 2 Tweeqs of 11 Tweeps
BONUS LINK
Twitter Handbook
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