Mobile App: Explore a U.S. city
UpNext offers highly realistic 3-D maps (complete with color-coded neighborhoods and block-by-block street representations) that let you check off filters to add markers for restaurants, hotels, and other services. Rare among app maps, these are accessible when you're offline. Right now the service is available for Austin, Texas, Boston, Chicago, New York, San Francisco, Washington, D.C., and Portland, Oregon, with six more cities coming soon.
Runs On: iPad, iPhone/iPod Touch.
Runners Up: Google Maps (free; Android, BlackBerry, iPad, iPhone, Symbian, Windows Mobile).