How to hide pasteboard in Illustrator CS5?

You can get a very quick, non destructive view of just the artboard area using the Navigator:

Go to Window -> Navigator and turn it on.

It’s not as handy as InDesign’s Preview or Presentation modes, but is is pretty handy.

EDIT: In response to @Scott’s comment, here are sample screen shots of how my custom [F9] key shortcut looks in practice.

Before: Lots of stuff outside the artboard:

After: I press [F9] and artboard flotsam be gone!

Hacking the Navigator in this way is not perfect, but it does the trick and is virtually instant.