I've just passed the SCBCD .. you can see what I've studied in the corresponding post ..
In my opinion the minimum requirements are the following:
1) study a book .. I read both 'EJB3 in Action' and 'O'Reilly EJB3.0'. I think that just one of them is enough (in my opinion 'EJB3 in action' is better if you are new about EJB, I have a little experience in EJB2.1 and I preferred the O'Reilly EJB3.0)
2) study the Mikalai Zaikin's SCBCD 5.0 Guide, it's very usefull (if you want a high score may be it's better to read the specifications too)
3) get a mock exam. I've bought the Enthuware EJBPlus and it helps me a lot. I don't know about the others.
In any case read the posts of the other ranchers and the Scbcd Links .. they are very usefull ..