http://folding.stanford.edu/Basically, if you're not folding, or running some other distributed-computing project, your CPU and GPU are just sitting there when you're not using them, like a dog in the basement, crying out for action. Think of your poor processor. It wants to cut loose. Give it something to do.
Okay: Fold with the basic CPU client and get ~100-200 points per day.
Better: Use PS3's Life with Playstation and get ~1000 PPD.
Best: Run the GPU3 client on a modern gaming rig and crank that for anywhere from 2000 to some 15k PPD for multiple high-end GPUs. Alternatively, run the advanced/slightly-experimental CPU client which does "bigadv" workunits if you have an 8-core. (I don't know much about that one)
Dwarfy: There's some absolutely gonzo setups out there. We're talking server racks with each motherboard having 3-4 high-end GPUs SLI/Crossfire'd together. PPD ranges from WTF to OMG. Some guy donated the use of 100-400 8-core computers to test the 8-core client and got 3M-9M PPD for it.
I have about 400k points donated on behalf of The Longevity Meme (Team 32461), an organization for immortality, and I'd love it if other people here joined. Someone is probably going to suggest a DF team, but unless we have a whole lot of power behind it, it's not likely to ascend the rankings much.
The general rule for distributed computing is simply "Leave it on". That's it. Nothing fancy, turn it off when you're running something that uses your computer extensively, but at all other times just let that thing cook indefinitely. (And dust out/ventilate your system or it really will cook.)