Nearby Tweets uses the Google Maps API to work out your location and show you Twitter users and Tweets for your location. You can use Nearby Tweets to find Twitter users who live near you. You can also search a word to find what people nearby are Twittering about that subject.
I actually set the location to the town where I grew up and found someone I went to school with - very cool.
Tmeet.me - send a Tweet about where you want to meet.
Swearing on Twitter Map - map of Tweets that have swear words.