The folks at Focalware have made a great app, killer! Focalware 2.0 takes it up a whole notch with there 2.0 version which takes advantage of the new iPhone 3Gs. 2.0 Update: The 2.0 update is available on the App Store. It includes compass support for the iPhone 3GS, integrated map for custom locations, and a major redesign. This update is free for all current users.
Focalware calculates the position of the sun and moon from rise to set anywhere in the world, at anytime of the year by utilizing your location and date information.
Focalware offers unrivaled accuracy and ease of use to photographers shooting outdoors.To say I use it a couple of times a day is an understatement!