I recently found this site called Foller.me which is a cool site to just find out general info on a particular Twitter user(s) This is great way to source certain user(s) on topical matters. I really enjoy using the Hashtag and cloud mentions of this App. There are many Apps like this including tweetstats.com but I just like the clean interface of Foller.me. The Tweet Analysis also gives you a more detailed anaylsis of the type of interactions you have with your followers. I really like the metrics of when a follower actually tweets and the "Attitude" feature. Great way to target user(s). Give it a try and tell me what you think. Did I mention it's free?