9-11 Commission Report
http://www.gpoaccess.gov/911/
This is the final (and official) report of the National Commission on Terrorist Attacks Upon the United States. The Commission’s Final Report provides a full and complete account of the circumstances surrounding the September 11th, 2001, terrorist attacks, including preparedness for and the immediate response to the attacks. It also includes recommendations designed to guard against future attacks.  

September 11 Web Archive
http://www.loc.gov/minerva/collect/sept11/index.html
"The Library of Congress, in partnership with the Internet Archive, WebArchivist.org, and the Pew Internet & American Life Project, has created a collection of digital materials known as the September 11 Web Archive. The September 11 Web Archive consists of over 30,000 selected Web sites archived from September 11, 2001 through December 1, 2001."

September 11, 2001 Documentary Project
http://lcweb2.loc.gov/ammem/collections/911_archive/
Online presentation includes almost 200 audio and video interviews, 45 graphic items, and 21 written narratives. Available for RealPlayer and MP3; an abstract of the content of each narrative is provided.

The September 11 Digital Archive
http://911digitalarchive.org/
Funded by a major grant from the Alfred P. Sloan Foundation and organized by the American Social History Project at the City University of New York Graduate Center and the Center for History and New Media at George Mason University, the September 11 Digital Archive is a project that uses electronic media to "collect, preserve, and present the history of the September 11, 2001 attack in New York, Virginia, and Pennsylvania and the public responses to them."

After September 11: Perspectives from the Social Sciences
http://www.ssrc.org/sept11/
This new site from the Social Science Research Council (SSRC) contains essays by well-known social scientists on the events of and following September 11. 

Annotated Bibliography of Government Documents Related to the Threat of Terrorism and the Attacks of September 11, 2001
http://www.odl.state.ok.us/usinfo/terrorism/911.htm
This impressive bibliography has been compiled by Kevin D. Motes (US Government Information  Division, Oklahoma Department of Libraries). It focuses on the US federal documents on terrorism and most specifically on attacks on the World Trade Center and the Pentagon. All documents are described with concise annotations and available through the Federal Depository system.

Center for the Study of Bioterrorism and Emerging Infections
http://bioterrorism.slu.edu/
Includes facts sheets, key articles, bibliography, case studies, official remarks, etc.

Centers for Disease Control: Public Health and Preparedness Response
http://www.bt.cdc.gov/
Includes information on bioterrorism and facts about anthrax, botulism, pneumonic plague, and smallpox.

C-SPAN's September 11 U.S. Response Archive
http://www.c-span.org/terrorism/
Here you'll find a searchable (short annotations) and browsable (topic, date) archive containing a large amount of C-SPAN's video coverage of events related to terrorism and the events of 9/11/2001. All video is viewable online.

Days after September 11, 2001
http://www.press.uchicago.edu/News/daysafter.html
The University of Chicago Press offers a series of essays "reflections by our authors in the aftermath."

Documents on Terrorism
http://www.yale.edu/lawweb/avalon/terrorism/terror.htm

September 11, 2001: Attack on America
http://www.yale.edu/lawweb/avalon/sept_11/sept_11.htm
The Avalon Project at the Yale Law School has put together these two pages to help those looking for primary texts related to terrorism in general or the September 11 events. The Avalon Project Website features documents in the fields of law, history, economics, politics, diplomacy, and government, and the offerings here reflect that span. 

Documenting the Tragedy
http://www.nyshrab.org/wtc/index.shtml
The New York State Historical Records Advisory Board points to archives, museums, libraries, organizations, and individuals who are creating digital repositories of September 11 documents, recordings and photographs.

Federal Emergency Management Agency
http://www.fema.gov/
Do a search on FEMA's web site for "September 11" to find information.

Legislation Related to the Attack of September 11, 2001
http://thomas.loc.gov/home/terrorleg.htm
The Library of Congress'(LoC) Web gateway to legislative information, has here collected links to legislation related to the September 11 attacks. This is a handy page for people looking for the exact text and disposition of bills.

National Library of Medicine -- MedlinePlus: Anthrax
http://www.nlm.nih.gov/medlineplus/anthrax.html
Includes news, overviews, diagnosis/symptoms, prevention/screening, specific conditions/aspects, and treatment.

One Year Later: The Fiscal Impact of 9/11 on New York City
http://comptroller.nyc.gov/bureaus/bud/reports/impact-9-11-year-later.pdf
Prepared by the Comptroller of New York City, this 65-page report offers an intensive look into the short and long term economic impact of 9/11 on the city.

The Peacemakers Speak
http://www.thecommunity.com/crisis/
Statements from seventeen of the Nobel Peace Prize Laureates made in the weeks following September 11.

Pentagon Information Page
http://www.defenselink.mil/pubs/pentagon/pentagoninfo.html

Research Buzz 911 Edition
http://www.researchbuzz.com/911/
A comprehensive set of links for disaster information.

Rumors of War
http://www.snopes2.com/rumors/rumors.htm
A collection of links to pages discussing the various rumors to come out of the September 11 terrorist attack on the United States of America. Each entry is followed by a date indicating the last time the corresponding page was updated.

Scholars of Islam & the Tragedy of Sept. 11th 
http://groups.colgate.edu/aarislam/response.htm
"statements, images, and links ... provided by the Study of Islam Section at the American Academy of Religion," speak out against terrorism and clarify the position of Islam.

Scout Report: Around the United States Campuses Reflect on 9/11
Information on the 2nd anniversary, 2003.

September 11: Interim Report on the Response from Charities
http://www.gao.gov/new.items/d021037.pdf
A report from the General Accounting Office.

A Sound WTC Remembrance
http://www.sonicmemorial.org/sonic/public/index.html
This project is a cross-media documentary of first-person accounts chronicling the life and history of the World Trade Center and its neighborhood before, during and after Sept. 11.  Beginning Wednesday, users will be able to search a database of stories and sounds from the site, which is part interactive sound sculpture and part dynamic audio archive.
Speech and Transcript Center: Transcripts and Speeches from September 11
http://www.freepint.com/gary/speech.htm
Has the statements of public officials about the disaster.

World Trade Center Information
http://www.ny.com/wtc.html

In addition to the web sites listed above, and the MILLIONS of articles published about September 11th, you will also find books and government documents in the CSULB Library.  Follow this search in COAST for the subject "September 11 Terrorist Attacks, 2001".