You could use the spare resources to run something like Folding@Home, which is a distributed computing project that uses donated spare CPU cycles to simulate protein folding. This is very important to medical research including developing new drugs and investigating the mechanisms behind cancer, Alzheimer's disease and various other conditions. I think it can use unused GPU resources too. You can visit http://folding.stanford.edu/
to find out more.
There are many other similar distributed computing projects out there, if this one doesn't appeal to you.