Mersenne@home is a Polish science project in the field of Mathematics, Number Theory, which, thanks to BOINC platform, uses Internet-connected computers to search for Mersenne primes. Mersenne primes are a numbers of the form 2p-1 and, in the current stage of research, counts millions of digits. Therefore, high computing power is needed to verify their primality.
If you want you can help in the search, by joining and providing your computer idle time. Mersenne@home is currently available for Windows, Linux and FreeBSD computers.
More information is available at http://mersenneathome.net/