Pocket Universe gives you observation tips and quizzes to test your knowledge about what you've seen.

App: Pocket Universe (Buy it for iOS here)
Price $2.99.

Pocket Universe is an especially great app for beginners. You can point your phone up at the sky to identify planets and stars near you, but the app also provides a list of suggested objects to observe based on the date. It even gives you a list of observation tips. Pocket Universe also has quizzes you can take on the planets, stars, and constellations so you can see how much you're learning.