Achievements and trophies are here to stay. It doesn't matter if you love them, hate them, or couldn't care less. Various forms of virtual rewards have shown up on the 360, PS3, Steam, Paradox Interactive titles (coming soon) and more. I personally like arbitrary proof that I've done something; small goals keep things interesting and don't cause a mess if you fail.
"Folding@home is a distributed computing project -- people from throughout the world download and run software to band together to make one of the largest supercomputers in the world. Every computer takes the project closer to our goals. Folding@home uses novel computational methods coupled to distributed computing, to simulate problems millions of times more challenging than previously achieved."
In short, it allows everyone to contribute to a very important research project about protein folding. The implications of successful research could find better treatments (or cures) for such things as Alzheimer's, ALS and many cancers. The distributed computing method is simple. Download a small program that can be run in the background of your computer. It uses your CPU's idle time to "number cruch" for Stanford's research. You'll want to turn it off for gaming but you won't notice a performance hit during web surfing, creating documents, and general computer use.
In addition to knowing your computer is doing a good thing, it also quickly becomes a task of reaching the next milestone (achievement). How many points can you average per day? How many work units can you complete in a month? I find myself tracking my stats more often than I'd like to admit.
Would you like to know more? Read more about the project here. All of the guides and help that you might need to get it running on your computer or PS3can be found here (among other places). The [H]ardOCP community even does giveaways for active members up to and including a new i7 machine. Why not put your lazy computer to work and contribute to something greater than yourself? I have it running on my work computer since I have to leave it on all the time. If it's just sitting there, I figure it could at least be doing something to offset the energy it's using.