The links on these pages are by no means comprehensive. They reflect my research methods and interests, which center on the U.S. and Europe.
Please feel free to propose additions or corrections to my lists, which I will revise as time permits.
Search for patents, U.S. Patent and Trademark Office—images of patents since 1790; requires a patent number or classification code for pre-1976 patents (see Carolyn Cooper's patent-finding tips)
Measuring Worth, EH.net site for exploring the value of various currencies by various measures