Available as of July 2004, The Ultimate WebCT Handbook: A Practical and Pedagogical Guide for WebCT 4.x arrived in my office last week. Measuring close to 600 pages, it looks like an excellent resource at first glance (especially to staff members who are new or relatively new to WebCT). Lots of detailed descriptions on each tool available and its advantages (For example, the section on the Quiz and Survey tool is a whopping 68 pages long! WOW!). Lots of "how to" sections that contain useful and detailled step-by-step instructions. Perhaps most useful and interesting are the sections that focus on best practices for online teaching. For example, common group work activities and assessment methods are discussed.
At $70USD + $10USD shipping it's not for every instructor (especially those with lots of experience working in this modality); however, it should be in every faculty lunchroom's reference section.