Wilson Huhn has posted an article discussing in detail the likely effects if President Obama were to have the chance to replace any of the five nonliberals on the Supreme Court. Huhn argues that a large number of cases would be likely to be overturned. He basically divides up the cases into those that he believes will be overruled and those who believes will probably or might be overruled. I generally agree with his assessments.
In the category of those he predicts will be overruled are:
Citizens United v. FEC (protecting under the First Amendment contributions from corporations and unions);
Zelman v. Simmons-Harris (allowing government to provide vouchers for children to attend parochial schools);
Van Orden v. Perry (allowing Texas to place the Ten Commandments on the state capitol under circumstances suggesting the non-religious message predominates);
NFIB v. Sebelius (five members of the Court concluding that the Commerce Clause does not allow Congress to mandate the purchase of health insurance)