I am looking for a shortcut to align the the text of layer B to the image on the background layer.

I currently eyeball this by using the rulers and grid, but feel there must be an easier or already defined solution to this.

If you have a selection you can hit 'v' to activate the move tool and then use any of the 'Align' buttons in the tool options bar to align your selected layer to the selection (http://help.adobe.com/en_US/Photoshop/11.0/WSfd1234e1c4b69f30ea53e41001031ab64-78c2a.html).

If you select the entire canvas (select all, cmd+a or ctrl+a on PC) before doing this then you can easily center a layer in the canvas. If you need a layer centered to another layer you can hold cmd (ctrl on PC) and click the layer to make a selection from the layer bounds and then use the above technique.