CS6 has a new feature that allows you to snap any layer's Anchor Point to its edges or center. You select the Anchor Point Tool (also known as the Pan Behind Tool previously) and depress the CTRL (Command on Mac) and move the ANchor Point towards the center and it'll just snap into place.
FWIW, this technique works for 2D and 3D layers.
You can do this numerically too if you Reset Transform>Anchor Point & Contents>Transform:(shape type)>Position.
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