Excellent Application for finding out locations of satellites, the international space station, etc.

Smart phones and tablets have made an unbelievable amount of information available at our fingertips. One of the greatest tools are astronomy tools, such as skycharts. Post a link to a page describing your favorite astronomy application whether it be on the iPhone/iPad, Andrioid, Blackberry or any other device. Make some notes on the page regarding the best features of this app. I'll give an example and we can go from there.