Though the White House clearly prefers to pass a health care reform bill with the 60 votes needed to prevent a filibuster in the Senate, a bill could also be passed by just 51 votes using budget reconciliation.
First Read gives an excellent "stripped-down, dumbed-down, Cliff Notes-like explanation of what reconciliation is, what hurdles opponents can place before it, and how it might be handled on the floor should Democrats decide to use it."