Via Eric Eggertson: Google Newsmap. Uses treemaps to visualize recent news stories, with apparently a very shallow hierarchy (Google's categories, then the stories themselves). Larger boxes represent stories from more sources, and darker boxes represent older stories. Colors represent categories. Checkboxes control which national version of Google News to use and which categories to include. Headlines only, but with popups giving the caption if one hovers over a headline. Very slick, interesting way to get a quick gestalt of the news.
I don't think I'd use it much myself, though — because of the shallow hierarchy, the treemap layout doesn't really convey a lot of information, it merely makes it difficult to scan through all the headlines on the page. And I'm not very enthusiastic these days about web sites that I have to check back on regularly in order to find new content, I'd rather use my RSS aggregator for that.