A team at the University of Alberta, led by Jonathan Schaeffer, has solved the game of checkers.  Through brute force calculations, they have shown that when played perfectly, checkers results in a draw.  As a consequence, their checkers playing program, Chinook, is now unbeatable by either human or machine.  Checkers is now by far the largest game ever solved.  For more on this result, see here, here, and here.