Due to the great interest in Java certifications, a number of web sites have sprung up. There are so many new ones that I am having to rebuild this list, so if your site does not appear here drop me a line email@example.com
Marcus has been running this site for almost as long as I have been running the LanWrights site. It includes mock exams, book reviews, an exam FAQ, discussion groups, and links to other related sites.
Test your Java skills with the Rules Roundup Game and discuss your certification concerns at JavaRanch. JavaRanch is also great for extensive discussion groups on non-certification topics such as, XML, Servlet/JSP, J2ME, and other Java related subjects. Many advanced programmers and book authors (including me!) hang out there to answer your questions. You might even win a free book in one of their frequent give-aways.
Huge list of mock exam sites, book reviews, study tips and news.
A. K. Gupta has provided a nice applet emulating the real certification exam, study notes, suggestions and links.