3rd dhtml menu type

So we have DOM based menus that do the tree collapse thing, and DOM based horizontal drop-down menus, but what about those sidebars that pull out lists to their right? I've been running out of room above the fold on my links page for some time now, and that 3rd type of menu is well suited for such out of control link collections.

Here's a first cut of a remake of my Links page. Rolled it out in like 30 minutes, so there are a number of things left to do:

1. figure out how to add the onmouseover and onfocus events using the DOM without adding IDs or classes to the links.
2. button styled links, which will bring up the cursor path problem (accidentally mousing over the button above and opening a different category on your way to the sub-list) which I'll have to mitigate with a setTimeOut.
3. if this is the left sidebar navigation instead of the main contents of the page I'll have to work out a way to hide the subnav, it never goes away as I've mocked it up here.
4. oh, and I guess it would be cool if the subnav could come in to the right of the particular nav item instead of all top aligned.