One tool available to use to answer that question is Tweetags - it is limited at present by being time-capped to search only the past 24 hours' tweets, but I expect as they grow they will start indexing a larger slice of time and therefore become much more useful.
Tuesday, January 20, 2009
I have a new blog post up at Biznology: The messenger is the message. New Media is Now Media, and if you aren't part of it you will be defined by those who are. How is US Airways being defined since The Miracle on the Hudson?