The source can be found at the eclipse-helpers project at sourceforge: https://eclipse-helpers.svn.sourceforge.net/svnroot/eclipse-helpers/fullscreen-commands
The plugin has been written for eclipse 3.5 but it works also for eclipse 3.4 although there are some problems with the handling of the toggle state of the commands...
When fullscreen mode is active all (main) windows are in full screen mode:
There is also a Toolbar button that can be enabled. Because the plugin uses the Commands Framework there are some unfortunate restrictions (bug 280033):
Once you have succeeded enabling the toolbar button, it will look like this:
I decided to hide the button by default, because in most cases the shortcut and the windows menu command should be enough.