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.
x10ephem computes sunrise and sunset times. It consists of a library and an assortment of utilities. The most useful utility is x10events, which parses crontab files and updates the time fields to track sun events. Combined with an X10 interface like HEYU or X10, this allows the scheduling of lighting events to follow the changing seasons and daylight savings time automatically. This application does not depend on X10; it can be used for any crontab entry you like.
SaVi is satellite visualization software that lets you create, run, examine, and modify satellite orbits in two and three dimensions. Simulations of Iridium, Globalstar, Galileo, GPS, and other satellite constellations are included. SaVi requires Tcl and Tk on a system with Unix libraries. SaVi works well with the 3D renderer Geomview. Geomview is optional, though recommended for its 3D rendering capabilities.
SAOTrace is a suite of software designed to simulate the as-built performance of grazing-angle X-ray optics using the ray-tracing approach. It is derived from portions of the NASA OSAC (Optical Surface Analysis Code) software suite. It can model nested conical as well as flat optical designs, and includes the ability to model arbitrary support structures and baffles. It can model non-ideal multi-layer reflective coatings as well as scattering from the optical surfaces.