http://www.autoacforum.com - Auto air conditioning forum.
The BrickBoard - Volvo mail.
Genuine Classic Parts - Licensed by Volvo to distribute parts for vintage Volvos. Site includes parts manuals for 1800s and other Volvos.
IPD Company, Inc. - Respected Volvo parts catalog company.
Karl Målberg's Volvo 1800 Picture Gallery - Many photos, owner's manual, more.
McMaster-Carr Catalog - Industrial supplies, from raw materials to component parts. Not Volvo-specific.
Old Air Products - Supplier of auto air conditioning parts. Online catalog, friendly sales staff.
P1800 List Forum - Broad-based support group for Volvo 1800 owners.
Volvo Club of America Texas Chapter
VolvoSolutions.com - Nice collection of manuals, etc.
V-Classics Interactive Magazine