Here are some valuable resources for Letterpress printing:
Briar Press the best portal for equipment classifieds, discussion area, downloads – ESSENTIAL!
NaGraphics great resource for printing supplies, Fritz Klinke owner, best for Vandercook supplies
Boxcar Press excellent site – fully investigate all the areas
AAPA excellent resource, especially the Resource Guide
Five Roses important information resource
Vandercook Press Vandercook blog
APHA become a member of the American Printing History Association
Adana and Kelsey UK supplier of rollers
Oak Knoll Press source for books about books, letterpress book source, etc.
British Printing Society excellent site with files for download on subjects we need to know
M & H Type buy lead type, and spacing material; in San Francisco, CA, USA
Skyline Type Foundry another source of lead type and ornaments, in Illinois, USA
Don Black Linecasting Service Canadian source for letterpress supplies
There is a man in Florida who sells printing supplies - send me an email message and I'll send you his email address (he does not have a web site).

Some Books:
Burke, Clifford. Printing Poetry: A Workbook in Typographic Reification. San Francisco: Scarab
Press, 1980.
Chappell, Warren, Bringhurst, Robert. (2nd ed. rev.) A Short History of the Printed Word.
Vancouver, BC: Harley & Marks, 1999. http://www.hartleyandmarks.com/
Dodd, Robin. From Gutenberg to OpenType. Vancouver, BC: Hartley & Marks, 2006.
Dowding, Geoffrey. Finer Points in the spacing & arrangement of Type. Vancouver, BC:
Hartley & Marks, 1995.
Gordon, Bob. Making Digital Type Look Good. NY: Watson-Guptill Publications, 2001.
Lawson, Alexander. Printing Types: An Introduction. Boston: Beacon Press, 1971.
Maravelas, Paul. Letterpress Printing: A manual for modern fine press printers. New Castle, Delaware: Oak Knoll Press, 2005.
Mitchell, M. and Wightman, S. Book Typography: A Designer’s Manual. Marlborough, Wiltshire,
UK: Libanus Press, 2005. Get from www.oakknoll.com
Morison, Stanley. A Tally of Types. Cambridge, UK: Cambridge U. Press, 1973.
Rummonds, Richard-Gabriel. Printing on the Iron Handpress. Oak Knoll Press, 1998.
ISBN 1-884718-40-x paperback. Most of the information is relevant to any type of
letterpress printing.

Printing Handbooks:
Hoch, Fred W. Handbook for Pressmen. NY: Fred W. Hoch Assoc., 1936. Many editions
over the years.
Lange, Gerald. Printing Digital Type on the Hand-Operated Flatbed Cylinder Press – 3rd ed.
Go to: http://BielerPressxi.blogspot.com/ for details. Important for photopolymer
platemaking and printing on the Vandercook cylinder press.
Mills, George. Platen Press Operation. Pittsburgh, PA: Carnegie Inst. of Tech, 1959. ESSENTIAL.
Check with NA Graphics for availability.