Invision - Prototyping and collaboration for design teams
Foursquare - Foursquare is all about helping you find new ways to explore your city.
Proto.io - Create fully-interactive high-fidelity prototypes in minutes that look and work exactly like your app should. Sign up for a free 15-day trial and get started.
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.
Balsamiq - Balsamiq. Rapid, effective and fun wireframing software.
Yellow Pages - YP.com local search connects you with over 19 million local businesses.