The SETI@home software has ...

There have been and still are various SETI projects (Search for Extraterrestrial Intelligence). The SETI@home project is only of those, but nonetheless there's something special with SETI@home. Due to a lack of funding for those usually cost intensive activities of scanning the space for remarkable radio signals and doing the analysis on the vast amount of resulting data, the SETI@home found a different solution from using data centers (it's driven as a non-commercial organization):

The project gets the radio data from the world's largest telescope, the Arecibo Observatory in Puerto Rico, and then distributes small portions of data to miillions of personal computers all over the world to get the data analyzed. People may download and install the free SETI@home software named "Berkeley Open Infrastructure for Network Computing (BOINC)" and then let it begin work on the data as soon as the computers has no other work to do (like a screensaver). The software automatically loads a fresh data package from the SETI server at University of Berkely, Californa, and starts analyzing. After the analysis is done, results automatically get sent back to the server in Berkeley. Effectively, the worlds biggest supercomputer consists of millions of privately owned and driven personal computers. Computer capacity, otherwise unused, gets used this way - without additional costs for anybody.

The interesting point is: It turned out that there are much more research projects from the realm of biology, physics, mathematics, capable to use this technology:

    Biology
          - Malaria Control — for stochastic modelling of the clinical epidemiology and natural history of malaria.
          - POEM@Home — models protein folding using Anfinsen's dogma

    Earth Sciences
          - Climateprediction.net — tries to produce a forecast of the climate in the 21st century.

    Physics and Astronomy
          - BRaTS@Home — to study gravitational lensing
          - Einstein@Home — uses data from LIGO and GEO 600 to detect gravitational waves.
          - LHC@home — simulates particles travelling in the Large Hadron Collider.
          - QMC@Home — uses Quantum Monte Carlo to predict molecular geometry.

    Mathematics
          - ABC@Home — attempt to solve the ABC conjecture problem.
          - SZTAKI Desktop Grid — searches for generalized binary number systems.

Dan Werthimer is chief scientist of SETI@home and of several radio and optical SETI programs at the university of California, Berkeley In the video at youtube, he explains the project.

Further Information:
The complete video is available at http://fora.tv
SETI@home project at UCB
SETI@home at Wikipedia