Starmap provides a list of suggested celestial bodies to observe each night.

App: Starmap (Buy it for iOS here)
Price: $4.99

Starmap has about 350,000 stars, 150 galaxies and clusters, and 50 asteroids and dwarf planets. The app gives you the "night's best selection" so you know what you should be looking for on any given night and it identifies shooting star zones. This app is also a point and locate that uses the iPhone's compass to identify the planets and stars right in front of you. You can zoom in on a particular object and the app has a night vision mode — the backlight on your phone dims and the images on the screen glow red so your night vision isn't ruined.