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.
Turn Off Filename Extension Warning
In Leopard, Apple fixed an annoying aspect of working with the Finder in Tiger. Previously, if you changed a file's extension, the Finder prompted for confirmation. But since no one has ever accidentally changed a filename extension, Apple thankfully added an option to turn that warning off in the Leopard Finder's preferences. Choose Finder > Preferences, and in the Advanced screen, deselect Show Warning Before Changing an Extension.