You may not be too familiar with Foursquare, a social app for your mobile phone that let’s you “check-in” to different places you visit. But if you’ve been interested in trying it out, now’s the time - from July 23 to July 31 jcpenney will donate a $1 dollar to the USO for every “check-in” to one of their stores up to $50,000! That’s in addition to the $1 million donation they’ve already made to the USO!

Need to know how to get started? Download one of Foursquare’s mobile apps on your phone. They provide apps for iPhone, Android, and Blackberry. “Officially unofficial” apps exist for Nokia’s S40, S60 and MeeGo platforms, along with Windows Phone 7 and Palm. If there’s no app for your phone, you can check in through Foursquare’s mobile site or via SMS. Once you’ve set up your Foursquare account, head on over to your closest jcpenney!

To check in, open the mobile app on your phone and Foursquare will use your phone’s GPS to find your current location. Click the ‘Check in’ button or tab to see a list of nearby places where you can check in. If the place you’re looking for isn’t in the list, you can search for it or add it directly from your phone.

When you check in, you’ll have the option to share your location with your Foursquare friends and with Facebook and Twitter. If you check in without sharing with your friends, your check-in will be private and only seen by you.

And while you’re there, be sure to let them know you’d like to round up your purchase to the nearest dollar for the USO. The difference will be donated to the USO too!