NPPA: Business Practices Toolkit:

I stumbled across this one in my browsing, a couple of days back - and keep finding more and more interesting content in it.

If you're looking at being a photog as a business, or you've already started, but are finding it a struggle to make ends meet, this is a good resource that, while it won't give you money directly, will help you understand where your money is going, and help you get more of it coming in.