Firefox: If you want to maximise the screen real estate you have — netbooks, anyone? — you could switch to fullscreen browsing in Firefox. What if you want to keep certain elements visible while you browse? Hide GUI Bar can help.
Hide GUI Bar is like a selective full-screen mode for Firefox. You can specify which elements will be hidden and which will remain like the menu bar, navigation bar, tab bar, bookmark bar and the status bar. Now if you need to keep the status bar visible but want the rest of the screen available for browsing, or any other combination of hidden and visible elements, you can do so.
The default hot key is CTRL+SHIFT+A but you can alter it to any other alpha-numeric combination. Hide GUI Bars is a free extension and works wherever Firefox does. Have a favourite tool for tweaking your display, Firefox-related or otherwise, let's hear about it in the comments.