Sheryll Oswald: eBay - forgeries, fakes, dodgy sellers, scams: the tip of the iceberg - educational articles for eBay buyers and sellers on forgeries, fakes, alterations and the problems of buying and selling in the Stamps category on eBay
Richard Doporto: Alterations, Fakes and Forgeries - closeup photos and detailed exposés of deperfs, reperfs, faked grills, removed cancels, etc.
Richard Frajola: Fraud On eBay – A Review Of The Stamp Category article
basestealer.com - an omnibus internet fraud link site
Fenton Smith: escrow sites - includes both valid and scam sites
Internet Fraud Complaint Center
StampChat - discussion board for issues important to the online philatelic community, including misdescribed items and fraudulent activities on eBay and elsewhere
eBay Stamps chat board - discussion board for general and specialised collectors on eBay
Frajola's Board For Philatelists - discussion board for philatelists around the world
Buying Tips for eBay collectors - don't get burned on your next eBay purchase!
The U.S. Philatelic Classics Society, inc. - Loaded with knowledge and resources related to pre-1895 U.S. stamps
"theswedishtiger"'s US Stamps - A pictorial guide - Need to know what any genuine U.S. classic stamp looks like?". Check the large, clear color scans on this site. Stamps are identified by Scott catalog number.