Heads up for those with plenty of spare computer cycles: the LIGO collaboration---that is, the scientific endeavour which is searching for gravitational waves---is offering a client for distributed computing to help in analysing parts of data of actual experiments. The client is called 'Einstein @ Home' and can be downloaded from
this site.
(I am not affiliated with Einstein @ Home in any way: I just happen to think this is a particularly sensible way of spending CPU cycles (apart from the computation of protein folding)---all that SETI and RC5-72 stuff is a waste of electricity, in my very humble but very definite opinion.)