Overall, Marcus Green references and javaranch references (and its mockup) helps much.
For
SCJP, I use Sun Certified Programmer for Java 2 Study Guide (McGraw-Hill Professional Publishing; ISBN: 0072132086). The book got a lot of questions (which is 2x harder compared to the real exam,
you should also check for the typo-error for this book, and there are 2-3 questions which got wrong answers).
I didn't buy book for SCWCD, I learned mostly from the
J2EE spec, J2EE tutorial, javaranch tutorial, free
JSP taglib tutorial, reading the WAR deployment descriptor and JSP taglib DTD.
For
SCJD, I use Java RMI book from O'Reilly and design
pattern from GOF. Java Design Pattern (downloadable pdf file) also help much
For SCJA, I use:
- Design pattern (GOF)
- Mastering EJB (Ed Roman)
- UML Distilled (2'nd edition) Martin Fowler
- EJB Design Pattern
- Sun Certified EA for J2EE (Mark Cade, Simon Roberts).
- Special Edition: Using Java 2 EE (QUE)