Some of the features in the upcoming Mac OS X 10.5 either already exist in present applications (as Dan pointed out), or developers have been inspired from Monday's keynote and are producing their own versions, with Web Clippings as our first example. The developer of Shrook looked at this new tool, realized that it's utilizing a fairly simple trick and whipped together his own Dash Clippings tool.
After playing with this for a bit, I can say it more or less works very similarly to the Web Clippings tool demoed in the keynote. You enter a URL into the widget, and it loads up the page. You then drag the widget to the proper size and over the specific area of the page you want to clip, and presto - you've just made yourself a live, dynamic web clipping tool that will check the page for updates as often as you tell it to.
Hey, who says Apple is the only company that can use the "good artists copy, great artists" steal philosophy? Once you're done answering that (or not), go snag yourself a copy of Dash Clippings and check one drool-inducing feature off your Leopard shopping list.