You can also turn off the screensaver part and it will continue to run as a background application. In fact, if you allow the screensaver to run, it slows down the data crunching considerably (if that is important to you). If you just want a neat screensaver, it can be that too.
You can join a SETI group so your calculations are added to a team total. We have a small group of SETI FReepers:
http://setiathome.berkeley.edu/stats/team/team_15327.html I forget who started the group, but you are welcome to join :-)