Just been playing around with some "Resizable" divs and you can get a really nice effect if you "stack" a number of the items and use them (for example) in the "west" region of a BorderLayout.

For example:

Code:
new YAHOO.ext.Resizable ('springy1', { height: 150, minHeight: 150, handles: 's', pinned: true, dynamic: true });
new YAHOO.ext.Resizable ('springy2', { height: 150, minHeight: 150, handles: 's', pinned: true, dynamic: true });

<div id="navigation">
<div style="height: 150px;" id="springy1">
  I'm springy 1.
</div>
<div style="height: 150px;" id="springy2">
  I'm springy 2.
</div>
</div>
It provides a really nice UI effect, now I've just got to work out how to maintain the sizes!

Gary

P.S. I found I had to set the height of the div explicitly cause otherwise it made them intially very small.