Here are some mac tips I know and consider "basic" mac knowledge, but no-one else seems to know.

• exposé key is on modern mac keyboards, looks like a load of squares on the F3 key.
• ⌘ + Exposé key => Show Desktop
• ⌃ + Exposé key => Show Application Windows
• ⌥ + Brightness keys => Open Displays prefpane in System Preferences.
• ⌥ + Exposé key => Open Exposé & Spaces prefpane in System Preferences.
• ⌥ + Dashboard key => Open Exposé & Spaces prefpane in System Preferences.
• ⌥ + Keyboard Backlight keys => Open Keyboard prefpane in System Preferences. (Only on laptops with keyboard backlighting.)
• ⌥ + Volume keys => Open Sound prefpane in System Preferences.
• ⇧ + Volume keys => Adjust the volume with the feedback noise setting toggled. If you normally have feedback "blips", it'll be silent. Or vice versa.
• ⌥ + ⇧ + Volume keys => Adjust the volume in 1/4 of a usual step.
• ⌃ + Eject key => Shows the Shut Down dialog.
• In the shut down dialog, hit R to restart, S to sleep, ⎋ to cancel.
• (Pretty much) Any dialog that pops up, hitting ⎋ will push the "cancel" button.
• In "Show all windows" or "Show application windows" exposé modes, hit the tab key to cycle through applications.
• Hit the space bar in exposé to activate "Quick Look" + windows pop up to 100% size as you mouse over them.
• Hold down ⌃ + ⇧ when mousing over the dock to toggle magnification whilst the keys are down.

(Alternative title Peter Cooper suggested, "A miscellany of input device co-ordinations to modulate the response of Apple's task preview and switching subsystem")