I completed this exam 2 weeks back and I found the Head First EJB by Kathy and Bert very useful. The exam objectives are presented in an easy to understand manner and to the point. Once you are through with that, you can do some mock exams in the book and in other sites like ejbcertificate.com and jdiscuss.com. That should be sufficient, I guess - you just need to get the concepts clear!!
All the Best, Regards, Nandini
Discipline, Dedication and Determination define Destiny.