I asked SpringSource this question and they replied that topics from the Core Spring 3.0 course could be used as the basis for what is needed in the exam:
I successfully passed the exam, however I can tell that those course topics are rather coarse and not really enough to prepare for all the questions that you should expect to see in the exam. To pass the exam, I also prepared for the more detailed topics from Core Spring 2.5 exam:
While preparing, I did not read any books. My only resources were Spring 3.0 Reference Documentation (dived deeply into it, especially into topics included in 2.5 and 3.0 exams) and my own experience in building Spring applications.