ABPS – Association of British Philatelic Societies
Germany & Colonies Philatelic Society
The Pre-Cancel Stamp Society (American)
The Precancel Stamp Society of Great Britain
“Swagbucks” Guide to Stamp Collecting (thanks to Amelia from Salt Lake City for this suggestion!)
https://www.uprinting.com/beginners-resource-guide-to-philately.html (thanks to Glenn from Vermont for this suggestion!)