There have been several services with smart phone apps release over the last year that encourages people to discover their community and to reward them for doing so.  These services allow people to check-in with their phones using their location such as at restaurants, shops, events, baseball games, etc., and to earn points or rewards for check-ins.

Services like Foursquare, Gowalla, Brightkite, Loopt, Yelp, and Whrrl are gaining users at a rapid clip.  In fact, Foursquare expects to hit its 1,000,000th check-ins per day in June 2010, and the number of check-ins grew by 50% in June.

Check-ins can be shared with friends in a service, and posted on Facebook and Twitter.  Once a person checks in they can creates comments, pictures, and recommendations.

These apps are fun to use and allow you to post real time so that your friends know where you are, what the place or event is like, and find more friends.

Businesses can also benefit from these services.  When a person visits a business and they check-in and share this with their friends, businesses and a map of its location are posted on these services.  Personal experiences that are shared can be a powerful social testimonial for a business.

Businesses are starting to use these services to engage with mobile customers by offering specials such as rewards or discounts for loyal customers. Businesses can also find local users.

Twitter now allows people to use their location, and this is coming soon on Facebook too.  Are you checking in yet?