Everytrail, a GPS-based app launched by a Palo Alto outdoorsman, features more than 400,000 outdoor paths around the world, from Barcelona to Los Angeles and beyond. Choose between guides created by professional writers and free user-generated tours. Nearby points of interest are illustrated (like an idyllic vista) with photos and background info. You can also track your own trips: the GPS monitors where you go and maps your path. And you can add photos and video to share online with other users.Cost: Free for user-generated guides; $1.99 professional guide; $3.99 Everytrail Pro (includes extras).