Visual Studio style Detachable Tabs
BCGControlBar Pro (MFC)
BCGControlBar for .NET
You can drag or tear-off any of the tabs with or without its content from the tabbed window and then it behaves as a floating or docking control bar. You can drop it onto any dockable area such as your application workspace or another docking control bar. You can also drag and drop windows to combine them in a docking window as new tabs.
Detachable tab windows provide an extremely flexible way to organize your workspace:
Visual Studio 2005-style tabs