Its all about the screen real estate...

All Glass Firefox
Autohide Statusbar. Hides/removes status bar from the bottom.
Fission. Displays links i hover over in the address box & also provides a page loading bar as shading in the address box.
HideCaption. Moves file menu & removes top windowframe, and adds appropriate window control buttons elsewhere.
All bookmark toolbar folders are icons, as defined in UserChrome.css, you can get more in then

Oh, and a UserStyle script to squeeze up the forward/back/reload/home icons a bit..
And Gmail Manager thrown in for good measure. a great extension
