Reading Josh Holmes blog, I ran across a reference to an article on the 12 Breeds of Client and How to Work with Them. It's a humorous look at different types of clients, including how to spot the type, the highs and lows for each type, and finally how to work with each type. It's an entertaining read. As with most prototypes, actual clients are combinations of the several types.
I also enjoyed FreelanceSwitch site which has this article. The site is targeted at a wide variety of freelance professions including designers, writers, programmers, illustrators, etc and the articles reflect this diversity. The articles are well written and concise. I also like the graphic layout of the site. It is easy to read and navigate and has a distinctive tone. The most recent article as I write this post is 7 Cheap Ways to Promote Your Development Skills, which has tips for developers seeking clients.