Good for GIMPS, 2⁵⁷⁸⁸⁵¹⁶¹ - 1 has a nice ring to it! GIMPS is one of the largest distributed computations in the world and have been tooling away finding primes since 1996. SETI@Home gets most of the credit for popularizing this kind of distributed computing, but GIMPS has been at it for even longer and has delivered consistent results.
What? Don't be silly. If they delivered no results or "nothing" at all, the project would have been shut down years ago. SETI has consisently reported that they have searched through a very large amount of signal and found only natural noise. That data is extremely valuable and is absolutely not "nothing".
If you want to run some distributed computing but don't like SETI@Home, give worldcommunitygrid.org a look. They run a number of projects aimed at curing stubborn diseases and working on clean energy and water. As a bonus, if you use it as your screensaver, the graphics for many of the projects are pretty cool.