Thanks to the recent version of Launch Bar (IMHO the finest App Switcher+ I've ever had the pleasure to use), their instructions for hiding the icon in the Dock appears to work for any application:
In order to get rid of the dock icon, you must modify the file named 'Info.plist' inside the Application's package (i.e. Sherlock.app/Contents/Info.plist). Open this file in your favorite text editor and add the following section (if it's already present simply change the 0 to a 1 in the string tag:NOTE: I substituted the standard square brackets for the purposes of posting here; you must substitute the angle brackets when editing. So far I've hidden my Sherlock and System Preferences icons. With the System Prefs you will have to write-enable the 'Info.plist' file by changing the permissions in a Terminal window:[KEY]NSUIElement[/KEY]
sudo chmod 464 /Applications/System Preferences.app/Contents/Info.plistEnjoy!
Mac OS X Hints