There've been quite a few topics on this subject already but to me it's still vague as to what's expected exactly.
I have a rather extensive background in webservices in general and an intermediate background in the JAX-WS, JAX-RS way of doing things. I have read the book suggested by the SCDJWS Links page and I found it ... lacking. I have done the java programmer certification (back when it was still sun) and it was a very technical exam which expected you to know all the ins and outs. In contrast this book is about as informative as wikipedia which begs the question: is the exam as "simple" as the book or is the book simply lacking in any real substance? If the latter is the case, is there a book that does prepare you adequately?
I heard J2EE Web Serices: XML SOAP WSDL UDDI WS-I JAX-RPC SAAJ JAXP by Richard Monson Haefel is a good reference book for this exam.
Also, Java Web Services Up and Running by Martin Kalin is a good one too.
But I am not sure if I should take the web service course from Oracle. It is too expensive.