Image via WikipediaSorta like Google Sky Map but with a lot more visual flair, Star Chart lets you explore the constellations in the sky and find out details about them.
In AR (augmented reality) mode, just start the app, then point the device up at the sky and look for matching things. It will highlight the constellations (complete with illustration and lines), as well as any significant astronomical objects such as galaxies, planets, and nearby stars. Pan the phone and let it act as a virtual portal. You can even engaged the red-tinted "night mode" to preserve your night vision.
In normal mode, just swipe / drag the view to desired spot. You can choose to hide or show lines, illustrations, and such.
Good app if you are an amateur star watcher, or have interest in the field. Good companion to a decent telescope. My only complaint? Size. Just over 2 MB download expanded to over 14MB app (according to Titanium Backup). Still, it's nice.