Visual Studio like MDI Windows Navigator
BCGControlBar Pro (MFC)
BCGControlBar for .NET
MDI Windows Navigator enhances "Ctrl+Tab" functionality (by default, when Ctrl+Tab keys combination is pressed, Windows just "swaps" 2 recently used MDI child windows).
Using this feature, you can display a scrollable list of all opened MDI children along with docking/floating panes and activate required document/pane.