As a social network, FourSquare is a creepy way to track friends at any moment of their day. As a food app, FourSquare is an amazing resource for scoring free stuff, and getting up-to-date reviews and insider tips. With the "top places" feature, you can see which bars and restaurants are buzzing in your area. And the best part? Many establishments offer incredible deals, from a free glass of wine, to an appetizer, just for checking in!