When you use Mission Control often, you’ll like the following defaults-write. It lets you immediately jump back to the most recently used Space. You can activate this option with a four-fingered double tap on the trackpad (or Magic Mouse). Enable the gesture with the following command:
defaults write com.apple.dock double-tap-jump-back -bool TRUE
To make the command take effect, you need to restart the Dock.
killall Dock
Revert to the default setting:
defaults write com.apple.dock double-tap-jump-back -bool FALSE
restart the Dock
http://www.youtube.com/watch?v=YDCzgdzu0t0&hd=1