I thought, at first, that this site had been thrown up after the release of The Lost Symbol because it contained so many of the bits of information that Dan Brown included. The site, however, is copyright 1998 and says "july02" in it's URL. Could this possibly be one of the sources of Brown's extensive research?
I wouldn't be surprised at all.
I also ran across this excellent summary of The Lost Symbol's plot.
Finally, this is one of the best book reviews I've ever seen on Amazon. It's hilarious and so very true. It's a one star review by Valannin "Pantheon Outcast" with the title "I'm pretty sure it went down like this" and it begins:
"Three years ago, Dan Brown and top executives in Hollywood and the publishing world assembled Thomas Harris, Dean Koontz, Michael Crichton, Paulo Coelho, Jimmy Wales, Abir Taha, and Rhonda Byrne in one room and said..."
The rest can be found on Amazon.