TheSaturn pages at SEDS, NSSDC, and JPL.
Cassini is a mission that left Earth on Oct 15 1997 and will arrive at Saturn in mid-2004. It will drop a probe into Titan, Saturn's largest moon, the only moon in the solar system with a dense atmosphere. JPL built the spacecraft, and has the main web site devoted to it. (It even includes instructions for creating your own model of the entire spacecraft.) The probe, named Huygens, may discover clues to the origin of life on the Earth. LANL also has pages on Cassini and Titan. The JPL page includes a description of nuclear safety and the Cassini power generators, and a message from Cassini program manager on this topic.