You can configure all of these things in System Preferences. For things like Spaces and Exposé, I believe the settings are under System Preferences → Keyboard → Keyboard Shortcuts → Exposé & Spaces if you are on Leopard or Snow Leopard. On Lion they are in System Preferences → Mission Control.
For things like adjusting volume, there are likely already shortcuts in iTunes (e.g. ⌘↑ and ⌘↓ for volume). You can also add custom Keyboard Shortcuts for any menu item in any application (or in all applications). Go to System Preferences → Keyboard → Keyboard Shortcuts → Application Shortcuts. Add a new shortcut, choose iTunes.app for the Application, enter the exact Menu Title (e.g. "Increase Volume"), and enter the shortcut you'd like.
Great news! I have one of the brand new SteelSeries Apex pro keyboards (the "first adjustable keystroke" keyboards) .. apart from being an astounding keyboard, yes, the novelty scroll wheel at the top right DOES adjust the master volume of the macbook. Dunno how they did it but it works. – Fattie – 2019-10-21T18:38:09.553
What's toggle switch? Use F1, F2, etc. keys as standard function keys? – Lri – 2011-08-05T13:16:10.007