Twitter analytic tool that allows you to analyze your Twitter followers. The tool allows you to see the percentage of Twitter followers who actually view and interact with your tweets, the male/female breakdown of your followers, and global and U.S location breakdown of your followers. The tool also provides a nice chart that displays the time of day you tweet, you get mentioned, and get retweeted.
Now this is the free version of the analytic report, but they do offer an Advanced Report for $9.99. It looks like you can sign up for $9.99 a month or at a yearly rate of $99.99. The Advanced Report will provide you sentiment analysis, a list of followers who engage with you, and a list of your top 20 most influential followers. Not too sure about the last two features, but the sentiment analysis report may provide some nice information about how you are being perceived in the Twittershpere.