If you don't use the Photographer's Ephemeris application, then I would strongly urge you to look into it. I use it all the time to figure out the sunrise and sunset times wherever I am, twilight times and also for figuring out where the angle of the sun will be during certain times of the day.
Stephen Trainor, the app designer will be releasing a 3D version of it soon, which incorporates a 'Google Earth' like view of the terrain so you can see how the light will fall on certain areas.
You can find out more about the current 2D version of TPE from the link below. It runs on most portable devices: