Hi Badranaya...
I've made a quite extensive search upon what I have for you.
The references of pdf files with be colored in red.
Patricia Crone: Meccan Trade and the Rise of Islam (large excepts)
http://books.google.ca/books?id=VWL-_hR ... ba&f=false" onclick="window.open(this.href);return false;
Patricia Crone & Michael Cook: Hagarism, the Making of the Islamic World (excerpts)
http://books.google.ca/books?id=Ta08AAA ... ca&f=false" onclick="window.open(this.href);return false;
Alfred Guillaume: The Traditions of Islam
http://www.answering-islam.org/Books/Gu ... /index.htm" onclick="window.open(this.href);return false;
viewtopic.php?p=151371#p151371" onclick="window.open(this.href);return false;
William A. Percy, Historical Facts about the Origins of Islam
http://www.williamapercy.com/wiki/index ... s_of_Islam" onclick="window.open(this.href);return false;
How Makkah translated the Assyrian area of Makkan & Melukhkha
viewtopic.php?p=152458#p152458" onclick="window.open(this.href);return false;
From ibn Warraq, Why I'm Not a Muslim (it went out of Internet)
viewtopic.php?p=146555#p146555" onclick="window.open(this.href);return false;
Dr Rafat Amari (good researches except when relying on the Islamic traditions)...
http://religionresearchinstitute.org/mecca/index.htm" onclick="window.open(this.href);return false;
On the Meccan Archaeology
http://religionresearchinstitute.org/me ... eology.htm" onclick="window.open(this.href);return false;
Mecca through the Classical Writers
http://religionresearchinstitute.org/me ... ssical.htm" onclick="window.open(this.href);return false;
Mecca and the Biblical Claim
http://religionresearchinstitute.org/me ... _bible.htm" onclick="window.open(this.href);return false;
3 articles: Is Muhammad a Descent of Ishmael?
http://religionresearchinstitute.org/Mohammad/index.htm" onclick="window.open(this.href);return false;
The Flowering of Muslim Theology (Josef van Ess, large excerpts)
http://books.google.ca/books?id=2MNvt1m ... &q&f=false" onclick="window.open(this.href);return false;
An interview with Karl-Heinz Ohlig, Muhammad as a Christological Honorific Title.
http://en.qantara.de/wcsite.php?wc_c=8052" onclick="window.open(this.href);return false;
A thread on his book: The Hidden Origins of Islam
http://www.faithfreedom.org/forum/viewtopic.php?t=56994" onclick="window.open(this.href);return false;
The Myth of Mecca, by Jack Wheeler.
http://archive.newsmax.com/archives/art ... 2943.shtml" onclick="window.open(this.href);return false;
http://debate.org.uk/topics/history/bib-qur/qurarch.htm" onclick="window.open(this.href);return false;
Ten Myths about Islam, by Timothy W. Dunkin
http://www.studytoanswer.net/islam_myths.html" onclick="window.open(this.href);return false;
viewtopic.php?p=85351#p85351" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/Criticism_of_Islam" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/Historicity_of_Muhammad" onclick="window.open(this.href);return false;
Mudarras Kadhir Gaznavi
http://www.reocities.com/spenta_mainyu/index.htm" onclick="window.open(this.href);return false;
Answering Islam Library of Classical Books
Including al-Kindi; Ignaz Goldziher; Arthur Jeffery; Alphonse Mingana; Joseph Schacht; William St. Clair-Tisdall.
http://answering-islam.org/Books/index.htm" onclick="window.open(this.href);return false;
Documents sur les origines de l'Islam (huge but in French, translator site required)
http://www.islam-documents.org/" onclick="window.open(this.href);return false;
Islamic books online (pdf files requiring Adobe)
http://islam-and-muslims.com/islamic-books-online.html" onclick="window.open(this.href);return false;
______________________
The easiest is to demonstrate that Muhammad was living in the Northwest Arabia, anywhere between Eilat and Hegra.
Certainly not where nowadays Mecca is located, but in the old area of al-Qura (6.92; 42.7).
Or how Muhammad has been fabricating, like shown in this thread.
A Resume of the whole thread
viewtopic.php?p=152903#p152903" onclick="window.open(this.href);return false;
Summing the Archaeological evidences against nowadays Mecca
viewtopic.php?p=150476#p150476" onclick="window.open(this.href);return false;
Completed in Resource Center:
MECCA -Myth vs Reality: In Search of Mt Sinai!
viewtopic.php?f=30&t=8527" onclick="window.open(this.href);return false;
Hadiths.
The next helpful thing is to use the Quranists' arguments debunking the hadiths, for without them 90% of the Shariah falls down.
Some Koraners sites:
viewtopic.php?p=124484#p124484" onclick="window.open(this.href);return false;
Mesmorial (Jared)
http://allpoetry.com/column/7554963-Min ... _-by-Jared" onclick="window.open(this.href);return false;
http://en.wikipedia.org/wiki/Criticism_of_Hadith" onclick="window.open(this.href);return false;
How the hadiths are copied from the Jewish traditions of Oral Laws
http://en.wikipedia.org/wiki/Oral_Torah" onclick="window.open(this.href);return false;
http://www.jewishvirtuallibrary.org/jso ... l_Law.html" onclick="window.open(this.href);return false;
The Criminals of Islam, by Shabbir Ahmed.
http://www.ourbeacon.com/wp-content/upl ... minals.pdf" onclick="window.open(this.href);return false;
Early criticism of the Hadiths:
http://www18.georgetown.edu/data/people ... -51827.pdf" onclick="window.open(this.href);return false;
Joseph Schacht, A Revaluation of Islamic Traditions.
http://www.answering-islam.net/Books/Sc ... uation.htm" onclick="window.open(this.href);return false;
How Muhammad's Sunna Trumps Allah's Book, by Sam Shamoun
http://www.answering-islam.org/Shamoun/ ... _quran.htm" onclick="window.open(this.href);return false;
__________________________________
Some of my threads in Resource Center:
External References to Early Islam
viewtopic.php?f=30&t=5285" onclick="window.open(this.href);return false;
Shirk & Idolatry in Islam
viewtopic.php?f=30&t=1062" onclick="window.open(this.href);return false;
Threads by Apple Pie, Rainbow & others over the Koranic Jesus
viewtopic.php?p=128793#p128793" onclick="window.open(this.href);return false;
The Case of Aisha
viewtopic.php?f=30&t=8159" onclick="window.open(this.href);return false;
Was the Bible corrupted?
viewtopic.php?f=30&t=8273" onclick="window.open(this.href);return false;
Imam Abraham & the son of the Promise
viewtopic.php?f=30&t=8369" onclick="window.open(this.href);return false;
Was the 'Ummi' prophet illiterate?
viewtopic.php?f=30&t=8381" onclick="window.open(this.href);return false;
Could the Vedic Varuna Be Allah ?
viewtopic.php?f=30&t=8394" onclick="window.open(this.href);return false;
The Laws (Sharia) Within the Koran
viewtopic.php?f=30&t=8384" onclick="window.open(this.href);return false;
The Koranic -ISA (son of...);
-Origin of the name; The Hindu connection; Ibn Maryama; The Word of Allah; Not Allah's walid.
viewtopic.php?f=30&t=8769" onclick="window.open(this.href);return false;
The Hadiths' Perfidy
viewtopic.php?f=30&t=8185" onclick="window.open(this.href);return false;
Abrogation in Islam
viewtopic.php?p=122827#p122827" onclick="window.open(this.href);return false;
viewtopic.php?p=154203#p154203" onclick="window.open(this.href);return false;
The Koranic Deceptive 'Proper Names' (still on-going)
viewtopic.php?f=30&t=10230" onclick="window.open(this.href);return false;
In Old Resource center....
The Cat's Archives
http://www.faithfreedom.org/forum/viewt ... 923#678923" onclick="window.open(this.href);return false;
Islam 101: A Lexicon for Dummies
http://www.faithfreedom.org/forum/viewtopic.php?t=34806" onclick="window.open(this.href);return false;
Was the Qur'an First in (pure) Arabic?
http://www.faithfreedom.org/forum/viewtopic.php?t=39999" onclick="window.open(this.href);return false;
The Islamic Declaration of Human Rights
http://www.faithfreedom.org/forum/viewtopic.php?t=38701" onclick="window.open(this.href);return false;
That's about it my friend, hope you find some requests therein... 
Authority has the same etymological root as authenticity.