Facebook will help you keep tabs on your friends' children, careers and concerts, but it won't tell you when your freshman year college roommate is at the cafe just around the corner, and it can't let you know that that stranger at a cocktail party is actually your sister's best friend.
That's news you can use, and a growing number of social discovery apps are here to help.
These apps marry your online social networks and information about your location to add an additional layer of data to the world around you. Services like Foursquare, Crowded Room, Ban.jo and Sonar are meant to spark serendipitous social connections between you and the people around you, or help you more easily get together with people you know.
Take a look at seven social apps that can help you make friends and the find the ones you already have: