Foursquare has been around since the release of Windows Phone but they have made some cool new improvements lately. They are utilizing the deep linking of the new secondary live tiles to pin specific places to your home screen. If you would like to see how to do this in your own application, you can check out my post on the subject here http://thesociablegeek.com/2011/11/09/live-tiles-in-wp-mango/.
Why is this cool? Well, if you are a FourSquare addict, then you can save yourself some time by pinning the place you go to the most onto your homescreen. 1 Click will Deep link you into that specific check in.
Besides my post (above), if you want more info on working with live tiles, check out the following :
Jeff Blankenburg has also created a post on Live tiles for his 31Days of Mango Series : http://www.jeffblankenburg.com/2011/11/11/31-days-of-mango-day-11-live-tiles
Or the Jump Start Video on Channel 9