Disraeli Gears (the web site, the album is fantastic too) is my favorite to just look at the many derailleur designs over the years and the history they represent:
http://www.disraeligears.co.uk/Site/Home.html
And from BF's own Mechanics Forum stickies, the quick link list that Sheldon assembled for us:
http://www.bikeforums.net/showthread...-com-shortcuts
Bill
__________________
Semper Fi, USMC, 1975-1977
I Can Do All Things Through Him, Who Gives Me Strength. Philippians 4:13