Newer keyboards:
F1: make the screen dimmer
F2: make the screen brighter
F3: show all windows (Exposé)
F4: show Dashboard widgets
F5: nothing
F6: nothing
F7: go back (in iTunes)
F8: play/pause (in iTunes)
F9: skip forward (in iTunes)
F10: mute/unmute all sounds
F11: make the sounds softer
F12: make the sounds louder
F13: nothing
F14: nothing
F15: nothing
F16: nothing
Older keyboards:
F1: nothing
F2: nothing
F3: nothing
F4: nothing
F5: nothing
F6: nothing
F7: nothing
F8: nothing
F9: show all windows (Exposé)
F10: show all windows for current application (Exposé)
F11: show the Desktop
F12: show Dashboard widgets
F13: nothing
F14: make the screen dimmer
F15: make the screen brighter
If the keys don’t do these things for you it’s probably because someone’s made some changes in your Keyboard preferences. Go to the Apple menu, then to System Preferences, then to Keyboard & Mouse, then to Keyboard Shortcuts. You’ll figure it out from there. Of course, if you don’t, you can always click here to send me an email.