The Court ruled 5-4 that the Second Amendment protects an individual right. Justices Stevens, Souter, Ginsburg and Breyer dissented.
From the Court's opinion:
In sum, we hold that the District’s ban on handgun possession in the home violates the Second Amendment, as does its prohibition against rendering any lawful firearm
in the home operable for the purpose of immediate self-defense.
The Court's decision can be found here.
Go read the opinion. I'm off to dance a little jig in celebration! :)