Google Sky App
A new app for phones powered by Google's Android software lets you travel through time. Google Sky Map lets you see the stars, planets and constellations in the past, or the future.
USA Today's Ed Baig checked it out. "The one limitation here is that you can only go back in time 100 years or go forward 100 years," Baig said. "That aside, it's a lot fun. It's going to appeal to amateur astronomers and really anybody else who loves gazing at the sky."
You can also point your phone at the heavens to learn about the stars above you. The app is free in the Android Market.