1. Foursquare - Checkin at a location and share it with your friends, including tips, special offers and photos. 2. Layar - Augmented reality browser/platform. Hold your phone in front of you and see where the nearest tweet is posted, where to buy Pizza - or what your search might be. 3. Lonely Planet iPhone City guides as we know them. 4. Google Maps - An oldie but certainly a goody. 5. CauseWorld - Do good while you turn your checkins into karma and donations. 6. Yelp - Search for places to eat, shop, play and get reviews from the local community. 7. Soundwalk - Get a real-time city tour on your iPhone based on your location - this is really cool!