Seti
SETI@home is a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence (SETI). You can participate by running a free screensaver that downloads and analyzes radio telescope data while you aren't using your computer.
The radio telescope signals are from the Aricibo Radio Telescope in Puerto Rico, pictured below.
Arecibo Radio Telescope
Seth Shostack / SETI Institute
Seti@Home
The Seti@Home Screen Saver
Here is a link if you would like to participate: http://setiathome.ssl.berkeley.edu/