There are so many websites covering US coins I couldn't begin to list them all. Here's 3 if you're interested in errors: 1) http://www.error-ref.com/ 2) https://doubleddie.com/ 3) http://www.varietyvista.com/ For a quick overview: https://en.wikipedia.org/wiki/Coins_of_the_United_States_dollar Google any denomination and you'll find multiple sites for the one you're looking for. Start off by doing what @Mike185 recommended. Buy a copy of the Red Book. Official name is "A Guide Book of United States Coins" by R.S. Yeoman, Whitman Publishing. Enjoy our great hobby.