I took the test on Saturday and scored 96%. I missed two questions. One on threads and the other one on Language Fundamentals.
The level of difficulty is about the same as Marcus Green mock exams.
The following helped me in passing the exam.
- A Programmer's Guide to Java Certification - Khalid A Mogul
- Sun Certified Programmer & Developer for Java 2 Study Guide
(Kathy & Bates)
- Velmurugan's notes (http://www.geocities.com/velmurugan_p)
- Mock exams on the net