ForeFlight is an iPhone app that is aimed towards pilots (both recreational and professional) rather than your average consumer. The app allows users to find nearby airports, maps, diagrams of airports, and lookup of plane information by tail number. The app also includes the A/FD, the Airport and Facilities Directory, which includes location data like field and approach information and location data on hotels.
You can download the app here for a whopping $69.99 (the highest price in the store).
ForeFlight iPhone appAdded: 7/14/08