This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
I have to agree with Paul here: Enthuware is, of all the mock exam products, the best in preparing for an exam. The way of asking questions is simular to the real exam and the level of difficulty is almost the same. (a bit more difficult then the real exam).
I have used it for both SCJP and SCWCD and I have always scored (slightly) higher in the real exam than in all of their mock exams.