Those trying to enjoy tape-delayed Olympic coverage will want to avoid NBC's Tweet Tracker. The mashup looks for Olympics-related terms, such as names of sports or athletes, then aggregates them to determine the most popular over a configurable period of time.
Simply seeing the most-discussed Olympics topics is interesting in itself, but the Tweet Tracker goes further. The Tracker uses Flash, which makes it incredibly responsive. It's pleasing to look at, mixing relevant images with a tag cloud for each topic. And it's fun to play with--you can click results to drill down, or drag the bar at the bottom of the graph to change the time range.
The results update every minute. With a status bar counting down the time until the next update, I find myself unable to turn away. This is the most fun and usable mashup I've seen in awhile.
Hat tip: Marshall Kirkpatrick