Very well known:
(1) Al Mihdhar (Malaysia, Able Danger)
(2) Nawaf Al Hazmi (Malaysia, Able Danger)
Reasonably well known
(3) Salem Al Hazmi (Malaysia)
(4) Al Shehhi (Hamburg - there's a quote somewhere (Joint Inquiry?) that the CIA figured out he was an Al Qaeda operative based on the 1999 intercept(s) - Able Danger, the nuclear thing)
(5) Atta (Hamburg, Able Danger, the nuclear thing)
(6) Jarrah (Dubai, Hamburg?)
Others
(7) Hani (Aukai Collins)
(8) Hamza Al Ghamdi (terrorist finance related to the Millenium Plot)
Link:
http://www.cooperativeresearch.org/context.jsp?item=a0900almarabhhazmaCheck out the entry for September 2000
(9) and (10) Ahmed Al Ghamdi and Satam Al Suqami (US customs investigation into terrorist finance)
Link:
http://www.cooperativeresearch.org/context.jsp?item=aspring01customsCheck out Spring 2001 (original material by everybody's favourite reporter Judy Miller)
(11) Wail Al Shehri (known to Middle Eastern intelligence service, probably Saudi)
One of the suspects named was Wail al-Shehri. According to a Middle Eastern intelligence source, he grew up in Khamis, near the Yemen border, attended teacher college there, and spent several years in an terrorist training camp known as al-Farouk run by Bin Laden in Afghanistan.
http://www.guardian.co.uk/wtccrash/story/0,1300,552472,00.htmland
I suppose Saudi intelligence could have gathered this information in the three days after 11 September, but I don't find it that likely - if they have the info on Wail, why not on Waleed and the other guys? Plus, Wail and Waleed obtained their new passports (in October 2000) through a relative in the passport office. If Wail's name was on the list of permitted travellers (the purpose of which was to stop terrorists and other troublemakers from travelling), why would he get a new passport through a relative? (the 9/11 Commission said that the passport may have been obtained in an illegitimate manner) One candidate hijacker, Khalid Saeed Ahmad Al Zahrani, dropped out because the Saudis knew he was a terrorist and refused to give him a passport (9/11 CR, p. 525). It's not a slam dunk, but I think the argument that Wail Al Shehri was known to Saudi intelligence is worth making.
Really, the fact that two of them are very well-known and the NSA was intercepting their calls from/to the States should be enough to blow the plot wide open. The other 9 are just a bonus.