Utwitbook is a new twitter-er search engine, it provides several advanced search features you might never met on other sites, e.g. design color search, followers range search, wefollow tags search....
Just some examples to get you started.
Find who relevant to sports, sports
Find who might be a designer, bio:designer
Find who located in New York, loc:(new york)
Find who set a myspace url, uhost:myspace
Find who named obama, name:obama
Find in the friends of some twitter-er, e.g. @utwitbook, fof:utwitbook
Find who set black style sidebar, clr_sbar:black