The SCJP 5.0 book SCJP Sun Certified Programmer for Java 5 Study Guide (Exam 310-055) by Katherine Sierra, Bert Bates , and the publisher is mcgraw hill is the best book for certification. This are my suggestions for SCJP 5.0 . The preparation can take different time for different people but for depending on their current knowledge of java. I read the entire book around 3 times and done all the exercises.
These are some tips from my side ..
1. Read this book don't look much here and there for jdk 1.5 whatever given in the book is quite enough.
2. Every chapter ends with two sections two minute drill (quick review) and practice exam. Two minute drill is very useful for last day reading and practice exam got very similar kind of quetions what you get in the real exam.
3. Exam given with the book is also very useful.
4. Take mock exams available for jdk 1.4 also and their you skip the applet and swing stuff because that is not in JDK 1.5
5. Practice exam questions available in the Book completeJava2 Certificaiton by Phil Heller (Sybex edition).
6. Prepare all scjp 1.5 mock exams available in JavaRanch.com
7. Practice More drag and drop questions. Around 15 to 20 drag and drop questions available in the real exam.
This are some useful links.
These two websites are having the best Java certification links and resource and community.