Marumushi.com has a fantastic News Map using the treemap visualization style. This is one of the best implementations of a treemap that I have found. Updated every 6 hours, it groups news stories (from the Google news aggregator) by overall category (technology, world, sports, etc.). You can choose to show the news map from 11 different countries, and the color shading of each block represents how old that particular news story is. Hovering your mouse over any square shows the whole title, and clicking takes you directly to the story.