Sunrise Calculation

The NOAA has a page describing the sunrise calculation here (pdf).

Jewish Calendar References

The algorithms for hebcal were taken from Emacs 19's calendar routines by Edward M. Reingold and Nachum Dershowitz. Their program is extremely clear and provides many instructive examples of fine calendar code in emacs-LISP.

Books

Understanding the Jewish Calendar
by Rabbi Nathan Bushwick. A well written treatment of the Jewish Calendar. Good bibliography.
Encyclopedia Judaica
Always the right place to start. Check out their entry on Calendar
Calendrical Calculations
Reingold and Dershowitz's own text. A keeper.

Other Good References

Hebrew Calendar Science and Myths
Fun stuff, page with neat-o facts about the arithmetic of the Jewish Calendar and its consequences.

Danny Sadinoff
Hebcal