I liked this feature in OS9 where I could drag a window to the edge of the screen and it would become a tab. Well, now you can do this in OS X thanks to StickyWindows. You can have multiple windows dragged around every edge of your screen, they can even be set as auto or manual tabs, and they support drag and drop. The application is shareware ($20) and a Universal Binary (in this latest version), you can demo it too before stumping up the very reasonable shareware fee.
