I have been using Awesome for a couple years now, and it has a great solution to this problem. You can add a rule to a window class (MPlayer creates a window wi

I have been using Awesome for a couple years now, and it has a great solution to this problem. You can add a rule to a window class (MPlayer creates a window with the class "MPlayer" for example) and set the "floating" property to true. The property can of course be toggled with a keyboard shortcut which is very handy with lots of terminals.