Robert let me know about Centrl which is another slick looking location based social network. The problem with most of these networks is that you need to have friends on them to be tempted to install it. Google got this easily with Google Maps since so many people already have it installed for Latitude. Centrl seems to be very similar where you can share you location with friends and let them find you.
The app differentiates a bit by helping you find new people and places to go around you that are happening. The most important feature in my opinion is that it lets you login with your Facebook, MySpace, Hi5, Ning, Orkut, Bebo or Friendster and it is integrated with Twitter. Personally I think that is a big twist in that you really do not need to register for their service separately from your regular social network. They also have iPhone and Android apps for you to keep tabs of your friends on those devices.