I don't know about you, but I find the Dashboard to be one of the most pointless parts of OS X. For some reason or another, I often find myself accidentally navigating to it.
The system settings have a checkbox that will actually take it out of Mission Control.
The only problem with this is that the Dashboard is actually still running. If you want to kill it off so that it's no longer taking up any of your system’s resources, then just enter the following into Terminal.
defaults write com.apple.dashboard mcx-disabled -boolean YES && killall Dock
If you ever need to re-enable it for any reason (why, I don't know), simple enter:
defaults write com.apple.dashboard mcx-disabled -boolean NO && killall Dock