Disney and Weta are both big on Maya for animation. Pixar uses their own custom software (Presto?) for animation, but I think character modeling is mainly in Maya. Also a bit of Z-Brush and Modo thrown in across the board, plus all the random software from The Foundry.

For effects most shops use Houdini.

I'm not aware of any major studios or effects houses using Blender, but that would be cool!