All,
I stumbled across a new (to me) component-specific website last week while trying to get my mind around vintage Sun Tour. Apologies in advance if this is already well-known to the cognoscenti.
It's called Disraeli Gears:
http://www.disraeligears.co.uk/
It is a well-done site, with an exhaustive listing by manufacturer (with good photos) of a lot of derailleurs
The opening page story explains how a certain album was named, and yes, connected to period correct bikes!
Dean Kernan
Pomona, New York USA