Posted By:
Josh K.This Board is the best place to start. Lipset's encyclopedia is another good souce:
http://cgi.ebay.com/Encyclopedia-of-Baseball-Cards-by-Lew-Lipset_W0QQitemZ5234148271QQcategoryZ26362QQssPage NameZWDVWQQrdZ1QQcmdZViewItem
Finally, consider a subscription to old cardboard magazine - see link above (the link above is also very helpful to identifying pre war cards).