OS X Yosemite is coming soon, and it moves the widgets from the Dashboard, which will be no more, to the Notification Center. But if you can't wait to get rid of it in Mavericks, here's how to do it.
Open up a terminal window, enter the following command, then hit RETURN. It's a good idea to copy and paste from this page.
defaults write com.apple.dashboard mcx-disabled -boolean true
Next, enter the following command, then hit RETURN.
After the Dock relaunches, your Dashboard will be gone.
To bring it back, repeat the process above, but change "true" to "false" in the first command (without the quotes). Here's my terminal session in which I first killed the Dashboard, then brought it back to life again.
This process only kills the visibility of the Dashboard, and doesn't affect the installed widgets. So if you later resuscitate it, all your installed widgets will still be in place.