Take a look at these Twitter sidekicks

Some other metric companies include TweetRush, which can give you an idea about the total volume (running about 300k people per day with about 5 Tweets per person); Tweetlists, which shows the most popular "conversations"; TweetVolume, where you can find the volume of a word or brand; TwitterGrader, which measures your rank (happy to say I am in the top 5% based on reach and authority); and Twitterrank, which for some reason does not rank me as high as TwitterGrader. (By the way, my Twitter address is mediadls.)