Navigating Column View Finder Windows in 10.6
One of the nice changes in OS X 10.6 is greatly enhanced keyboard navigation of column view windows in the Finder.
In 10.5, if you wanted to move up and down the hierarchy of a column view window, you had to use the Left and Right Arrow keys--right to drill down, and left to move back up. To move within a given folder in that column view window, you could either type a few letters of the target file's name, or use the Up and Down Arrow keys to move through the list.
While this worked fine, if you wanted to move back up a hierarchy--say to check on a file in a higher-level folder--the system would close each folder you had drilled down into as you moved backwards. (The alternative is to use the horizontal scroll bar to see the off-screen columns, but this means reaching for the mouse.) This functionality made it a real pain to get back to where you started, as you'd have to again use the combination of arrow keys and/or letters to select your desired folder.
In 10.6, you can still use the arrow keys to navigate in this manner, and they behave exactly as they did in 10.5, opening and closing folders as you move down and up the hierarchy. But 10.6 adds support for navigating column view Finder windows with a new set of keys: Tab and Shift Tab.
While these keys appear to work just like the Left and Right Arrow keys do, there's one key difference in their behavior in column view windows. When you use Shift-Tab to back out of a drilled-down into folder, the system leaves those folders open, with the path to the open folder shown by gray backgrounds on each of the parent folders, and on the currently-selected file. (In list and icon views, Tab and Shift-Tab select files by alphabetic name.)
So after navigating back up a folder hierarchy, you can get back to exactly where you started by pressing the Tab key again a few times. Even better, though, is to mix the new keys and the old keys: instead of pressing Tab a few times to return to your starting point, just press Right Arrow once, and you'll jump all the way back down to the presently-selected file. (If you use this shortcut, you'll find that it also moves down one file in the target folder; just press Up Arrow to get back to the originally-selected file.)
For those of you who prefer keyboard navigation in column view Finder windows, the Tab/Shift-Tab key pair can save you a ton of time when navigating those windows.