Heads up - it's geek-out time now. One of the things that's always bugged me about Photoshop is that there is no keyboard shortcut for showing/hiding the current layer. A lot of times, I like to quickly do some before/after checks to see if the adjustment layer I just added is working. Usually I'm clicking on the show/hide eye icon to do this.
The most recent version of CS6 supports conditional actions. So now you can do something akin to "if this, do that, otherwise do that". This is perfect for creating a show/hide layer option. Here's how to do it:
First, create 2 actions. One is called Show Layer, and the other is called Hide Layer. For the Hide Layer action, have a new layer selected (anything other than the locked background layer), start recording the action, and then go to the Layer menu and select Hide Layers. Stop recording. For the Show Layer action, do the same thing, except make sure the layer is not visible when you start recording the action.
Now that those actions are created, create a new action called Layer Toggle (or whatever) and start recording. For the first step, click the arrow at the upper right of the action palette and select "Insert Conditional". The conditional action window will pop up. Make it look just like this:
Stop recording and give that action a keyboard shortcut. You should now have 3 actions like this:
And you're done! From now on, when you hit that shortcut, Photoshop will look to see if the current layer is visible. If it is, it will make it hidden (and vice versa). I've got this assigned to a button on my Wacom tablet and it's working great.