I run SETI@home because I've been running it off and on since I was a freshman in high school. :) Seriously, though - it's nice to be a part of something so massive. Plus who knows, something might be found someday.
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.