Fox News just called Ohio for Barack Obama. Obama is on pace to win every Kerry state plus (at least) New Mexico and Ohio. Barring shocking results in Kerry states west of the Mississippi, Barack Obama will be the next president of the United States.
By the way, Nate Silver's FiveThirtyEight.com predicts that it is literally impossible for John McCain to win the election without Ohio.
Update: The other nets have called Ohio, too.