Planets is a fun, interactive program for many-body gravity simulations. The emphasis is on play: it's easy to add in planets, zoom in and out, change the physical constants, save and load configurations, etc. It's designed to be easy enough for a kid to enjoy, but that hardly precludes adults.
wmJupiter is a Window Maker applet which features the planet Jupiter. It allows you to keep track of the Great Red Spot and the current distance in astronomical units (AE). The four Gallileo moons (Io, Europa, Ganymede, and Calisto) are also displayed when they are near the planet.
setirotate automatically spawns the SETI@Home commandline client, rotating it through work units in a work unit cache. You can configure the number of work units to store, the number of processes to run simultaneously, the number of simultaneous result-upload/workunit-download transfers, the time interval within which its allowed to perform said transfers, and the timeout interval for when a transfer fails. It will immediately start working on a work unit when the previous one finishes, while uploading the newly finished result (if the upload interval permits) in parallel. It strives to always keep something running.
Astro Info is an astronomical ephemeris/almanac for PalmOS. It displays some basic information useful to stargazers, such as rise, trans, and set times, coordinates, magnitude and phase information for Sun, Moon, and the other 8 planets and stars. It can display a view of the sky (with stars, the Sun, Moon, and planets positioned) at arbitrary times and locations. You can also search for objects based on their names and see where they are.
Multi-body Gravity Simulator (MGS) allows you to perform a simulation based on a fixed time slice. Its unique features are the ability to perform realtime simulations, a three dimensional visualization of the simulation, and the ability to design simulations in XML and with a GUI. The accuracy of realtime simulations will depend on your machine speed. Fixed time step simulations are also supported.