NASA
Nasa: Sts 107 (Space Shuttle Columbia)
NASA.gov provides information regarding the Space Shuttle Columbia disaster. Content includes crew biographies, press releases, shuttle images, and scientific data and research.
Other
Spacefilght Now: Nasa Studies Telemetry for Signs of Orbital Impact
Article from February, 2003, reports on a possible object that might have separated from Space Shuttle Columbia that might have caused the disaster. Since this article, it has been found that a piece of foam did fall off of Columbia.
FOX News
Fox News: Nasa: Sudden Rise in Temperature Detected Before Breakup
Article from February, 2003, reports on problems with the landing, debris field, etc.