I use a big external monitor at work, and carry my MacBook around. I've found that Spaces is not much needed when I have two monitors rather than one. However, bringing up Spaces System Preferences panel just to toggle Spaces on and off is a pain.
So I wrote a small AppleScript that toggels Spaces on and off:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080730095923129