Astropulse is a scientific experiment closely related to SETI@home. (SETI@home is a program that helps SETI while you aren't using your computer - read more about it at its node.)
Stephen Hawking predicted that black holes evaporate in a burst of energy - and that the universe used to be filled with many more black holes that have since evaporated.
To detect the dying gasps of black holes, we need to do a lot of computation - perfect for SETI@home-style distributed computing. We already have plenty of data from SETI@home observations at Arecibo, but the calculations are different from those done by the SETI@home client (in fact search for the opposite kind of signal). So Astropulse is another distributed computing screen-saver program. It uses a platform called BOINC, to which SETI@home is being moved as well.
Astropulse is currently in Beta testing. You can read more about it at: http://www.planetary.org/html/UPDATES/seti/SETI@home/Update_110501.htm