"Folding" has been around for a few years. You install the client software the organization provides on your computer and it allows them to distribute data to your system. It gives them far more resources for modeling, calculations, and rendering on a larger scale than they would otherwise have with their own equipment. Medical research (particularly cancer) is a popular application if you're not into looking for little green men.
It's not a big deal unless you're worried about your electric bill since your computer runs at 100% the entire time.