Firefox: If you're on a small laptop or netbook, you know how precious vertical screen real estate can be. Tabs Always In Titlebar is a handy little Firefox extension that does exactly what it says.
Once installed, you'll see your tabs have moved up into the title bar space, much as they do when you maximise Firefox. It makes it a little hard to move the window, but you can adjust how much space exists between the tabs and the top of the window, which is handy. Hit the link to try it out.