Remove the Dock
If you are are one of those people who hates the dock, you probably already know it is fairly easy to remove it for good. However when you do this you also lose other features such as Exposé, Command-Tab switcher and Dashboard. A much better solution is to move the dock to the top of the screen and then hide it - making it invisible, but still around.
The easy way to do this is to download a copy of Tinkertool (free) that allows you to modify lots of hidden preferences.
The more hardcore solution is to use the terminal. Before you start, make sure Dock hiding is off by going to the apple menu, choosing Dock then "Turn Hiding off" . Alternatively open up the dock section of system preferences and turn hiding off there, or control-click on the gap in the middle of the dock (or even press Command-Option-D).
Then launch the terminal (located in Applications/Utilities) and type
defaults write com.apple.Dock orientation -string top
and press enter. Nothing will happen at first, until you log out then in again or restart the dock process in Activity Monitor (also located in Applications/Utilities).
Once you do this you should see your Dock appear at the top of your screen, and all you need to do is turn hiding off again, and your Dock will be invisible, only activating if you hover over a very thin line below the menu bar.