Runme.org is a software art repository, launched in January 2003. It is an open, moderated database to which people are welcome to submit projects they consider to be interesting examples of software art. Previously.
Jason Freeman created N.A.G. (Network Auralization for Gnutella), which turns peer-to-peer keyword searches into chaotic audio collages. Also, my favorite METAMIX, which algorithmically remixes user-selected source material into new music. They are both incredibly fun, and useful(be you a musician) programs. Also, runme.org and generative.net are two fun sites that host links to a cavalcade of software art.