I discovered today a genial component by Joan Garnet, the SplitPane component.
It uses the Macromedia ScrollPane component as basis and it has lot of really useful features.
Some of them I read from the blog post:

• nested of SplitPanes within each others
• orientation: horizontal or vertical
• enable/disable component
• event driven component
• max/min width/height
• separator state (expanded/collapsed)
• separador size
• references to each component of the panel
• expansion direction ( leftRight – rightLeft, topBottom – bottomTop )

See a demo of the SplitPane component here
http://www.joangarnet.com/…/release_v2_fram_1.php