I have been a supporter of SETI@home for about five years. When I started there was not an easy way to participate in multiple projects. A few years back BOINC (Berkeley Open Infrastructure for Network Computing) was developed for the home user to volunteer their personal computing power and time.
See the basic info below from the BOINC site.
Use the idle time on your computer (Windows, Mac, or Linux) to cure diseases, study global warming, discover pulsars, and do many other types of scientific research. It’s safe, secure, and easy:
Download and run BOINC software
Enter the project URLs, your email address, and password.
This is a simple process, so sign-up today.