I used the Head First Servlets and JSP book to familiarize myself with the JSP 2.0 and Servlet 2.4 specification. It's an awesome book, though some topics like Design Patterns are a little weak. In such cases, although Wrox doesn't have a 310-081 book out (that I'm aware of), their 310-080 is a huge complement for such cases.
I understand the Head First Servlets and JSP book just came out in Aug. 2004, and is one of the first books, if not only, out there for the 310-081
If you do use a 310-080 book, don't waste too much time on the SingleThreadedModel as it has been deprecated.
I'll be taking the test this weekend and will let you know if those resources were enough to pass the exam.