Everybody and their mother has written a Twitter-based app, but I haven’t seen any so far that try and help you find other Twitterers that you’d find interesting, so I made one.
It’s called “Twits Like Me” – just enter your Twitter screenname in the search box, and the Twits Like Me search engine will try and find other users that Twitter about the same things that you do. I’ve found that at least a few of the ten users it returns are interesting enough that I’ll start following them, but it is still in its infancy, so your satisfaction may vary.
Twits Like Me is constantly updating its search index, so the results should become more relevant over time. (You can get information on updates to Twits Like Me by subscribing to the Twits Like Me RSS feed or the main RSS feed for my blog.)
Oh, and thanks to the guys at Twitterholic for unknowingly providing a design. ;-)