Window Tabs

That's it really. Extend the idea of tabs for document windows, like Firefox and others, to the whole application window.
A right click on a window border allows a pre-defined size of tab to be dragged out to an arbitrary or pre-defined width. The tab has the application name and/or the document name on it. This would make it much easier navigate around multiple apps open on the desktop.
Yes, I know you can use the little buttons on the task-bar - but I generally don't. I find it easier to arrange overlapping windows so each one that I need to access has at least one edge visible at all times. The tab idea would allow for more than 4 be to arranged like this. Colour-coding could be optional to allow for grouping.