Some personal examples:
-Select a layer, hit cmd+A, and click the center align button will center the layer to the canvas.
-With the eye dropper tool, click anywhere on the canvas and drag off screen to select a color from outside of Photoshop.
-cmd+] takes layer forward, cmd+[ takes backward. cmd+shift+] takes a layer to the front, cmd+shift+[ takes it to the back (I use this way more than I thought I would).