File this under awsome. A while back I posted an idea about having an ABC or Heatmap scrollbar. The idea was that you could show suplimentary information in the scrollbar area. Turns out that the recently launched Google Chrome uses a similar UI in their "Find" UI.
As you search you can see the matching occurances of the keyword in your document. I love it and hope there is a way to extend this so after visiting a search engine I can see the matching words on the resulting page.