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 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. Over 1013 first zeroes were checked. After the results have been analyzed, the project administrator has stated that they will be posted on the American Mathematical Society website.