I run SETI@home (at least I used to, I can't connect to the new one) because if we discover an alien race, it will be the most important event in the history of the human race.
SETI@home and Astropulse are funded by grants from the National Science Foundation, NASA, and donations from SETI@home volunteers. AstroPulse is funded in part by the NSF through grant AST-0307956.