Check out this very cool mashup using Twitter and Google Maps.
Alessio Signorini, PhD Candidate in Computer Science at the University of Iowa, created it. He says:
Every 25 seconds this page monitors the stream of tweets containing Swine Flu related keywords (e.g. “swine”, “Tamiflu”, “flu”) and plots their locations on the US map.
Each colored dot represent a tweet related to a certain keyword. If you click on it, you will be able to see the author and the text of the tweet. Enjoy!