Here’s a tip for avoiding those nasty out-of-memory warning dialogs. One of the reasons Photoshop needs so much memory is that by default it keeps a snapshot of the last 20 things you did to your document, thus allowing you to undo your previous 20 steps. (You can see the running list of your last 20 steps in the History palette.) As you might expect, storing 20 steps takes a mighty chunk of memory, and if you’re running a little low (or getting those evil out-of-memory warnings), one thing you might try is lowering the amount of steps Photoshop stores. In Mac OS X, go under the Photoshop menu, under Preferences, under General, and you’ll find a field for History States. (In Windows you’ll find Preferences under the Edit menu.) You can lower this number (try 8 States for starters), and you may avoid the dreaded memory warnings. Just remember, by lowering the States, you don’t have 20 undos anymore.