I carry a PocketPC type PDA with me when I'm out shooting. I downloaded a program by Jonathan Sachs (the guy who wrote Lotus 1-2-3 and Picture Window image editor, and a photographer himself, http://www.dl-c.com/) called Ephemeris that is good for this very thing. It will tell you the phase and rise- and set-times of the moon and sun, and will also calculate the elevation and azimuth (compass direction, with magnatic variation inlcuded) of the sun throughout the day selected. It takes a few tries to find the porper time of year for an exact location of the sun, but if you want the angle the next day it will tell you the time. See a description of the program here: http://www.luminous-landscape.com/reviews/...pocket_pc.shtml
Sachs has also written an existing light program, and a depth-of-field calculating program, both for the PocketPC and for the Palm devices.
For the PC there are a number of astronomy planetarium type programs that will do the same thing. Check download.com and search for 'astronomy'.
And to toot my own horn, I've written a (mostly) freeware database applet for recording photo information that runs on the SprintDB database on a PocketPC: http://handango.com/PlatformProductDetail....=1&platformId=2 It contains most fo the functionality of Sachs programs (though slower) except for the ephemeris.