If you have a full screen application and you don’t want the dock to get in the way (such as iMovie 2), set the LSUIPresentationMode in your info.plist to 1 as is below:
<key>LSUIPresentationMode</key>
<integer>1</integer>
If you wish to remove the MenuBar also (but still have them available if you if you mouse near them, set the value to 4).
Source: http://developer.apple.com/documentation/MacOSX/Conceptual/BPRuntimeConfig/Concepts/PListKeys.html