Marie Loughran’s new book How to Start a Home-Based Jewelry Making Business looks like a great resource. she covers loads of topics including book keeping, ethics, marketing, employees etc.
If you have been enjoying your craft and playing with th idea of turning it into a business or are looking for a new starting hard economic times (The NYTimes says economic downturns are a good time to be entrepreneurial) this might be a good resource.
If you have a bit more cash to spend, think about the Jewelry Business Diploma at the GIA, which can be completed in a few online semesters.