I've been running SETI@Home solo on-again and off-again since 2004 (this is my second account after losing my first). I was -- and still am -- fascinated by the idea of a legion of computers working together toward a common goal.
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.