Collecting Error Coins  
   Just as nearly every family has its black sheep, virtually every coin series has its failures. These are known as errors or mis-struck coins, and have a following all their own.
   http://studium.com/6/errorcoins.html

Israel Error Coins  
   The site focuses on Israeli error coins but also features Canadian, U.S. and others. See bi-metallic errors, coins struck on scrap metal, and others.
   http://www.geocities.com/israelerrorcoins/

Silver Dollar VAMs  
   Detailed information on silver dollars, specifically Morgan and Peace Dollar die varieties known as VAMs.
   http://www.robjoyce.com/vams

Combined Organizations of Numismatic Error Collectors of America  
   National numismatic organization devoted to error and variety collectors.
   http://conecaonline.org/

Error Coins Magazine  
   Monthly magazine devoted to error coin collecting. Available by subscription.
   http://www.etcmmag.com/

Jason's Error Coins  
   Images of a collection of error coins. Wheat cents, Mercury dimes and other assorted.
   http://www.geocities.com/jasonscottcraton/index.html

Baker Numismatics  
   Photographic image library of coins with doubled dies, repunched mintmarks, over mintmarks, and repunched dates.
   http://www.bakercoins.net/learn/images/

Canadian Error Coins  
   Information and some images of circulating errors, including an overview of die varieties. Site in English and French.
   http://members.attcanada.ca/~err/index.html

World Error Coins  
   Describes and illustrates dramatically mis-struck foreign coins. Includes information on recognizing various types of error coins as well as articles on how to get started collecting eror them.
   http://www.worlderrors.com/

Rotated Die Coin Census  
   Census for US coins with major die rotation of 90 degrees to 180 degrees, includes Fake error detection and measurment indices.
   http://www.RotatedDies.com