If you use the hidden Dock feature in Mac OS X, you can speed up the time it takes to show the Dock. The command removes this delay.
defaults write com.apple.Dock autohide-delay -float 0
To make the command take effect, you need to restart the Dock:
killall Dock
Revert to the default setting:
defaults delete com.apple.Dock autohide-delay
Screencast: