One of the most comprehensive coin books ever printed has been made available for free online by U.S. Rare Coin Investments. The book? Walter Breen's Complete Encyclopedia of U.S. and Colonial Coins

I owned the book but it was so huge and unwieldy I didn't get much use out of it. As it's now out of print, I sold mine for $150 (having paid $89) on Amazon. I perused the site and it has all the high-resolution images that I remember. Having this book online is a valuable addition to the numismatic knowledge base.

(via Susan Headley)