JQuery :: LivingStories Partial Scroll Menu?

I was wondering if anyone had already built the jQuery equivalent of the menu on Google's livingstories that scrolls with the page to the top then sits at the top until the page is scrolled back down. If you haven't seen it, here's an example [URL}.. It doesn't work in IE, but in other modern browsers, the menu on the right ("Timeline of important events") starts out 450+ pixels down the page, below headers and other page chrome, but when it would otherwise scroll off the screen it switches to "position: fixed; top: 0" If the whole thing does not fit on the page, as you scroll near the bottom it switches again to "position: relative; top: NNNpx" where NNN is presumably the difference between the position of the top of the footer and height of the menu.

It's a nice effect that I haven't seen before, and I was wondering if anyone had already created something like this as a jQuery plug-in.