Rena has a wonderful site filled with a tremendous amount of information. Many of her articles are also applicable to other types of art work.
She also has published some e-books, the latest of which is Social Networking: Sell Your Jewelry Online. I purchased Your Profitable Jewelry Booth and was very pleased with it.
Be sure to check out her sections on Your Jewelry Website, Jewelry Displays, Jewelry Party Tips, and Jewelry Show Tips. These articles (and there are many) are most helpful to beginners, but even seasoned jewelry artists can get some good info here. I wish I'd known about this site before I started selling jewelry.
Her blog, Jewelry Business Blog has some interesting info as well. One recent article detailed how a jewelry thief was able to steal jewelry from upscale stores, often right under the clerks noses.