Photography...
... just kidding.
Take my advice (from personal experience): if you want to have money to spend on your computers, do
not get seriously interested in photography. It will leave you with nothing to spend on your systems (just hope they don't break, or you won't be able to afford to fix them). :Q
Anyway, I am personally involved in Folding@Home, but also have a machine on SETI at the moment to help them finish ahead of BBR (then everything goes back to F@H after SETI 1 ends). There are many other good projects, including SoB, United Devices, Distributed Folding, SETI@Home, Climate Prediction, Distributed Particle Accelerator Design,
et al.