The InfoNode Docking Windows framework contains an extensive list of features. InfoNode Tabbed Panel is a central component in the framework wich means that most features of that library also apply to the docking windows framework.

Noticeable Features
The window classes are Swing components, making them easy to integrate with your Swing application.
Support for heavyweight components (requires Java 1.5, see InfoNode Docking Windows Developer's Guide).
Can be used in applications, web start applications, applets etc. Does not require any sequrity permissions (note: needs permission for the hover mechanism to work).
Windows can be dragged, minimized, maximized, undocked, docked and closed, and then restored to their original location.

InfoNode Docking Windows default look (using InfoNode Look and Feel)

Undock windows to floating windows that can be moved anywhere on any screen. Add menu bars to the floating windows.
Virtually no limitations to the window layouts that can be created. Unlimited depth of nested tab and split windows.
Experimental Look and Feel Docking theme that tries to replicate the look of the active look and feel. This may or may not work depending on the active look and feel.
Read and write window layouts, including modified property values.
A powerful properties system that allows almost all visual and behavioural aspects of one or multiple windows to be changed.
Custom components can be added to window tabs, view title bars and tab windows. This make it possible to add application specific buttons.
Window bars at the edges of a root window which contains minimized windows.
Advanced mouse hover effects.
Customizable window buttons and popup menus.
Visual themes can easily be created by modifying property values. A number of different themes are included in the distribution. The themes can be seen in the demos and the screenshots.
... and many more ...