How to Use Foursquare?
Foursquare is an online service that lets you share your existing geographic location with your friends using your mobile phone or even a desktop web browser.
If you are in the US, you can also update your location on Foursquare via text message. You can use squares anywhere in the world.
The square apps for iPhone, Blackberry, Android and Palm use GPS to show a list of nearby locations. If you have moved more than any other place, then you are known as “Mayor” of that place.