I came across this site today, courtesy of a RT by @sarabozich:
It’s an automatic Tweep aggregator (that’s right; it’s a Tweep aggregator, not a Tweet aggregator). It locates Twitter users near you. It uses a combination of Twitter and Google APIs to geographically assess your IP, translate it to a physical location, and correlate that with the location of other users nearby. It’s pretty slick, and what with all the talk about maintaining a list of Central PA Tweeps (often coupled with talk about how we’re all too lazy to do it ourselves), pretty convenient.