In an apparent trend set by some of their latest work for the US online media, like the MTV Award Twitter Tracker, data visualization firm Stamen Design recently released an interactive treemap [nbcolympics.com] showing the tweets that deal with the current Winter Olympics in real-time.
A subtle (almost invisible?) sparkline on the top shows some stats and the relative amount of tweets over time. The larger the rectangle, the more tweets have appeared about that topic. Individual rectangles can be selected for more detailed tweets about that specific topic. More information is available on the Stamen blog.