SpaceX Falcon 9 Lander - Try (and fail) to land Elon Musk's SpaceX rocket
Foursquare - Foursquare is all about helping you find new ways to explore your city.
SpaceVR - Explore space with Oculus Rift (pre-launch)
Tripadvisor - The Tripadvisor mobile app is available for the Android and iOS platforms. It can be used to create reviews of hotels, restaurants, and to chat with other travelers on Tripadvisor forums.
The Size of Space - An interactive visualization of the universe
Yellow Pages - YP.com local search connects you with over 19 million local businesses.