AreaFace is a reverse Google Map mashup. Instead of taking your friend/follower list and placing them on the map, you click the map down to any area and it gives you the recent Twitteres that list themselves in that location/area. A great way to find more people using Twitter around you.
You can also search for keywords and trends to find locals (or wherever) talking about a topic that interests you. I tested some and found some new poeple to try and follow.