* Astronomy

STARDUST@home is similar to the SETI@Home program.

Although the program is not up and running - there is still 50 days left till the stardust probe returns - you can register for the program.
Here is their website:

http://stardustathome.ssl.berkeley.edu/

The Stardust probe had a dramatic encounter with Comet Wild-2, passing just 240 km away from the mountainous ball of ice, rock and dust, two years ago.
The craft sent back startling images of the object and grabbed particles streaming away from its nucleus to return to Earth.
The flyby occurred in deep space 389 million km from Earth at 1944 GMT, 1 January, 2004

Scientists say the probe's data will yield valuable information on the early history of the Solar System.
Dust from Wild-2 was scooped up by a robotic collector filled with aerogel - a very low-density glass - and stowed inside a sample-return capsule.
This will be delivered to Earth on 15 January, 2006; the capsule making a soft landing at the US Air Force Utah Test and Training Range.