Distributed computing is the process of running a single computational task on more than one distinct computer. This differs from cluster computing in that computers in a distributed computing environment are typically not dedicated to distributed computing, whereas clusters are almost always comprised of dedicated hardware. This makes distributed computing very attractive because it utilizes computational resources that would otherwise be unused.
Two popular non-profit distributed computing projects are distributed.net and SETI@home. United Devices is the largest commercial distributed computing network. Some will venture that Distributed.net is not a non-profit project since the main RC5-64 project they do is indeed for a cash prize from RSA Labs. Many others exist, such as the popular Genome@Home and Folding@Home
Distributed computing works so well because users like to see stats and the even though the client may be using 90% or more of their CPU, it runs at an extremely low priority so that it only uses power that would be wasted anyway.
Distributed computing is also an active area of research with abundant literature. The most known distributed computing conferences are The International Conference on Dependable Systems and Networks  and the ACM Symposium on Principles of Distributed Computing . Journals include the Journal of Parallel and Distributed Computing .