ZetaGrid
ZetaGrid was at one time the largest distributed computing project designed to explore roots of the Riemann zeta function, checking over one billion roots a day.
Roots of the zeta function are of particular interest in mathematics, since the presence of even a single one that is out of line with the rest would instantly disprove the Riemann hypothesis, with far-reaching consequences for all of mathematics. So far, every single one of them has failed to provide a counterexample to the Riemann hypothesis.
The project ended in November 2005 due to instability of hosting provider.[1] Over 1013 first zeroes were checked.[2] After the results have been analyzed, the project administrator has stated that they will be posted on the American Mathematical Society website.[3]