A scientific plotting library for C/Fortran built on cairo
A 2D scientific plotting library built on cairo. Provides uniform output to pdf, ps, png and X-Windows. Written in C with no dependencies (other than cairo) as a direct replacement for PGPLOT.
2D Gravity simulator, including a simulation of the solar system
This application started out as a study of Newtonian physics, but evolved into a 2D simulation of the solar system. (Viewed from the south, because Jupiter just wouldn't be Jupiter without the great red spot.) The source code is available for developers who would like to make their own customizations and unique scenarios - like sending a black hole through the solar system. For the casual user, this program allows you to truly become familiar with the solar system.
JPARSEC is a Java Package of Astronomical Resources for Standard Ephemerides Calculations, focused on accuracy, documentation, 2D/3D charts, realistic planetary rendering, and Astrophysical modeling. For source code visit http://conga.oan.es/~alonso/