as promised, the Splitter can now do vertical splitting as well as horizontal.

Also, I’ve implemented minimumSize for the panels.

An example:

The HTML for the above is this:

<div id="splitter_wrapper" style="height:200px;border:1px solid #000">
  <div id="topleft">top left, minimum height 50px</div>
  <div id="bottomleft">bottom left, minimum height 100px</div>
  <div id="right">right, minimum width:50px</div>
</div>

and the javascript is this:

var horizontal=new Splitter($("splitter_wrapper"));
var vertical=new Splitter(false,{orientation:1});
vertical.addWidget($("topleft"),{minimumSize:50});
vertical.addWidget($("bottomleft"),{minimumSize:100});
horizontal.addWidget(vertical);
horizontal.addWidget($("right"),{minimumSize:50});

The Splitter class requires Mootools. You can get the class file here.