A StreamGraph is shown for the latest 1000 tweets which contain the search word. The default search query is 'data visualization' but a new one can be typed into the text box at the top of the application. You can also enter a Twitter ID preceded by the '@' symbol to see the latest tweets from that user. A parameter to the URL can be used to specify the initial search word. For example, use http://www.neoformix.com/Projects/TwitterStreamGraphs/view.php?q=coffee to see the latest tweets about coffee.
Update on Nov 16th, 2009: You can now enter twitter lists in the format @nytimes/staff in order to see the latest 1000 tweets from every user defined in that list.
The StreamGraph shows the usage over time for the words most highly associated with the search word. One of these series together with a time period are in a selected state and coloured red. The tweets that contain this word in the given time period are shown below the graph. You can click on another word series or time period to see different matches. In the match list you click on any word to create a different graph with tweets containing that word. You can also click on the user or comment icons and any URL to see the appropriate content in another window. If you see a large spike in one time period that hides the detail in all the other periods it will be useful to click in the area to the left of the y-axis in order to change the vertical scale.
Credits go to Lee Byron for the visual ideas behind the StreamGraph (although I'm using a simpler symmetrical form), to Processing for the development tools, to Martin Porter for the Porter Stemming Algorithm, to Vaga for the two small icons, and to Summize for building a great API into the Twitter data.
Updated on June 15th to support returning more data for Twitter ID queries (for example: @JeffClark ).