The following sites are recommended:
Imaginative Book Illustration Society (IBIS): www.bookillustration.org
(For book search) International League of Antiquarian Booksellers: www.ilab-lila.com
Antiquarian Booksellers Association: www.abainternational.com
Provincial Booksellers Fairs Association (PBFA): www.pbfa.org
The Ephemera Society: www.ephemera-society.org.uk
Quad Royal: vintageposterblog.com A very interesting blog about all aspects of posters.
And for any country blues enthusiasts: a 24 hours country blues internet radio station (Juke radio):
www.weeniecampbell.com