Free software projects
Relatively active & supported
Evolvotron - "Generative art" software to evolve images.
Fracplanet - Generates fractal terrain or planets.
Obsolete / Dormant
Voluminium - Experiments with efficient rendering by adaptive image sampling
Sudoku - Python code for sudoku puzzle solving (and creation).
Various Java applets (source not actually online anywhere currently).
He who receives an idea from me, receives instruction himself without lessening mine; as he who lights his taper at mine, receives light without darkening me. That ideas should freely spread from one to another over the globe, for the moral and mutual instruction of man, and improvement of his condition, seems to have been peculiarly and benevolently designed by nature, when she made them, like fire, expansible over all space, without lessening their density in any point, and like the air in which we breathe, move, and have our physical being, incapable of confinement or exclusive appropriation. Inventions then cannot, in nature, be a subject of property. Society may give an exclusive right to the profits arising from them, as an encouragement to men to pursue ideas which may produce utility, but this may or may not be done, according to the will and convenience of the society, without claim or complaint from any body.-Thomas Jefferson, letter to Isaac McPherson, 1813
The characteristics of information be it software, text or even biotech research make it an economically obvious thing to share. It is a non-rival good: ie, your use of it does not interfere with my use. Better still, there are network effects: ie, the more people who use it, the more useful it is to any individual user. Best of all, the existence of the internet means that the costs of sharing are remarkably low. The cost of distribution is negligible, and co-ordination is easy because people can easily find others with similar goals and can contribute when convenient.-"The economics of sharing" The Economist Feb 3rd, 2005