The Clone Source Panel
This panel has a couple of neat features for people who spend a lot of time in cloning. You can now set up a series of preset areas in the Clone Stamp tool. Simply click on one of the icons at the top of the Clone Source panel and Option-click (PC: Alt-click) on a point. That will save that location to the first icon. Click on the second icon and do the same thing. Now you can save a series of location points and go back by just clicking on the icon.