A series of audio recordings were released by the Federal Aviation Administration (FAA) and the North American Aerospace Defense Command (NORAD) that detailed the aviation response on September 11, 2001. The New York Times has created a page that allows you hear the tapes with a rolling transcript. Kudos to them for doing this. They also have an article that explains the release. Rutgers University Law Review has also released a more complete transcript with downloadable MP3 files.
Do yourselves a favor and listen. We must never forget what happened on that awful, awful day.