libAstronomy provides a set of astronomical routines to ease the calculation of ephemerides. It includes mathematical functions to compensate various astronomical phenomena like precession, nutation, etc. The getconstellation routine finds the constellation for a given coordinate. It also calculates the positions of the sun and moon in two different precise ways.
MultiSeti is a utility for the Seti@Home client which helps you manage multiple SETI packets. If you have dial-up access to the Net, want to download more than one packet, and don't want to run clients simultaneously, MultiSeti will run one after another (when one is finished analyzing, it starts seti to analyze the next packet).
pscal is a simple shell script that creates PostScript calendars. It's not the most advanced calendar creator available, but for quick, nice looking calendars, it's very handy to have sitting in your bin directory. Features include: font selection, user-defined holidays, phase of moon, and days past/remaining in the year.