While it's very cool and all the Dashboard does consume quite an amount of memory. The following commands enable/disable Dashboard as noted here:
To turn the Dashboard off copy the following to a terminal window:
defaults write com.apple.dashboard mcx-disabled -boolean YES
To turn Dashboard back on execute the following:
defaults write com.apple.dashboard mcx-disabled -boolean NO
follow either command above with the following to restart the Dock:
I'm seeing around 100MB of RAM freed up by turning the Dashboard off.