Pebble has updated their app to version 2.0, bringing a completely new interface, along with the Pebble appstore and the Pebble 2.0 software. The store lets you find several watch faces and apps, including Foursquare and Yelp, all in one place. Since the Pebble can only hold eight watches and faces at a time, your unused apps will be stored in your App Locker, and you can swap apps at any time.
Note that updating your Pebble to 2.0 will remove any watch faces and apps not built for the 2.0 software, while the Pebble app will offer to update any faces and apps that are compatible automatically.
For more on the Pebble 2.0 and the Pebble appstore, be sure to check out Adam Zeis' coverage over at Smartwatch Fans!