Sunrise Sunset does exactly what its names says for iCal. It computes the times the sun rises and sets and produces an iCal calendar containing those events. It is based on a little Basic program that did the sunrise and sunset calculation and has been gussied up with a better user interface and an iCal output back end. It is moderately accurate, so unless you are timing your sunrise or sunset experience to the minute, it can be quite useful.
Sunrise Sunset user interfaceThe interface is simple. You enter your latitude and longitude. Go to Google if you can't figure these out and don't have a GPS. North latitudes are positive; south latitudes are negative. East longitudes are positive; west longitudes are negative. Those are the coordinates for Port Angeles, WA in the example to the left.