The Photographer's Ephemeris

"The Photographer’s Ephemeris (TPE for Desktop) is a free application for Mac/Windows/Linux designed for landscape photographers." (Credit: Stephen Trainor, software developer.) There are two requirements for the program to function on your computer: Adobe AIR (free) must be installed; and your computer must have an active Internet connection. There's plenty of online support, including tutorials (with text and graphics) and video tutorials. In my opinion, the videos for iPad are especially well done and should help to give you a good sense of how the application works and what it can do.

Editor's Note: "TPE 2.0.2 for iOS" ($8.99) is a universal app for Apple iOS mobile devices (iPhone, iPod touch, iPad).