The Suppressed September 11th
Recommended Reading Concerning 9/11
It is important to note the intentional cognitive dissonance where the notion of "conspiracy" is derided nearly every day in the media, yet that same media's own reports indicate that conspiracy was the most likely scenario on 9/11/01.
In the Crimes of the State article, No George Monbiot, These are the Facts of September 11th 2001, I detail 70 areas of interest with links to sources. There are more anomalies, but these are a solid framework for beginning a study of possible US government conspiracy which either allowed the attacks to occur, or actively participated and made the attacks to occur.
For those with plenty of time and interest in this subject, Paul Thompson's Complete 9/11 Timeline is an exhaustive and comprehensive collection of mainstream news reports from around the world. Thompson's work has been an indispensible source for numerous researchers.
The original timeline of suspicious activity, produced in late 2001 by Michael C. Ruppert was called, "Oh Lucy! You Gotta Lotta 'Splainin to Do." Several entries can be taken in more than one way, and much more data has emerged since that time.
A relatively new website called WantToKnow.info maintains several pages of these collections of news stories. Some of their included stories don't appear on other sites, and so it is recommended to check out their offerings.
I highly recommend the 911proof.com website, as they provide sourced evidence organized by topic in easy to access web pages. I have come across some material there I hadn't previously seen, such as specific quotes from firemen on the scene in New York City that day.
Physics Professor Dr. Steven Jones maintains the Journal of 9/11 Studies where you will find some technical arguments, and some lengthy papers authored by academics.
Several recommended books are David Ray Griffin's The 9/11 Commission Omissions and Distortions, Nafeez M. Ahmed's The War on Truth as well as The War on Freedom, Professor Michel Chossudovsky's War and Globalization, and Daniel Hopsicker's Welcome to Terrorland.
There are of course other authors and other books and other websites with value, such as 911truth.org, for instance ... but ...
Now For the NOT RECOMMENDED
I would be remiss if I didn't warn new researchers about the minefield of nonsensical garbage out there on the Internet, supposedly put out by "truthers." Anyone can label him/her self as such, but that doesn't make it so.