I've started a list of nifty Alt (or Option) key tricks I use in my day-to-day editing.
You'll find it by visiting my Ask Damien page, and looking in the "Docs" section in the right-hand column.
The Alt key is a wonderful little resource. You'll find lots and lots of little time-savers and handy shortcuts when you Alt-click on things in Photoshop and Elements (and ACR, for that matter). In fact, it's fun just to randomly Alt-click on stuff to see what happens!
If you have any favourite Alt/Option key tricks of your own, please add them to my list! I'll be adding more, too, as I think of them.