One of the books that I am currently reading is
Photographer's Market: Guide to Building Your Photography Business. So far it has been quite good.
I also recommend the
Prophotolife.com blog. It is a new blog that discusses the business of photography as well as some technical and DIY topics. He has compiled his first 14 posts into a PDF "book" you can download that all discuss the topics you need to consider when starting a photography business.
Edit: You might also want to pick up the Photographer's Market book as a general reference to selling photographs.