If you want considerable detail and history on a specific dance within an 'era', I commend to you the following site:

http://www.streetswing.com/histmain.htm

From there you can go on (by letters of the alphabet) to considerable info on a dance history, famous performers, etc...

Diagrams are more difficult, but depending upon your choice of a specific dance, can be found.

This reply is late in your timeline, but let me know if you have more specific need that can be filled right away.