My Friend Kevin told me about this site called GIMPS which is used in the search for Mersenne primes.

On November 17th GIMPS member Michael Shafer at Michigan State
University proved 2^20996011-1 prime. At over 6.3 million digits it is
easily the largest known prime number, beating GIMPS' 2 year old
record of just over 4 million digits. You can read more about the
discovery at the GIMPS Home page, http://www.mersenne.org

Congratulations to Michael and all GIMPS members for our sixth success!
Good luck to all in the search for the 41st Mersenne prime! With a lot
of luck you could even share in the $100,000 EFF award for finding a
10,000,000 digit prime!!

Well maybe it's too late - since if you follow the link above you'll see that the 41-st Mersenne Prime has already been found!