A number of people wrote to whack on me for claiming the Tab key was related to the metal tabs on a mechanical typewriter, saying instead that it is short for "tabulator," a device for making tables. In that sense the key name still makes sense on the computer keyboard, although I wonder if people would have thought that before Word came up with its table feature. On systems with monospaced fonts (and even on Macs with proportional fonts), many people still use the space bar to make tables.
Cull Graphics Quickly with Preview
You're faced with a folder full of images, and you need to sort through them, trashing some number and keeping the rest. For a quick way to do that, select them all, and open them in Preview (in Leopard, at least). You'll get a single window with each graphic as an item in the drawer. Use the arrow keys to move from image to image, and when you see one you want to trash, press Command-Delete to move it from its source folder to the Finder's Trash. (Delete by itself just removes the picture from Preview's drawer.)