This is similar to one of the ideas I talk to Claire about, it uses the geocode on tweets to locate them on a map of the world, this one marks them with a blue dot on a map of the USA during the Obama inauguration, it also allows you to filter by two words and assign them a colour red or blue, so you can have good / evil in blue and red or Obama / McCain for example. It also allows you to scrub through the time line so you don’t have just a static image you can see quarter hourley snapshots of tweets across the united states, the image above shows Jan 21st 2009 – 12:00pm EST.
I like this method of showing information, on the map and the way you can do red vs blue comparisons.
This person has also created other similar Twitter visualisations using processing and the Twitter API.