Resin offers a free developer lic. and has really good support. It is very developer friendly and offers good EJB 2.0 support.
Here is another good free tutorial on EJB... EJB CMP/CMR tutorial Here are some comments from people who read the tutorial... What people think: Achim from Germany writes: "I read your white papers "Introducing EJB-CMP/CMR" part 1 and part 2.... These papers are the best start for EJB.... Now I'm very interested in part 3 (and 4), but I can't find them on the developerWorks Homepage ..." (They are coming soon.) Pete from North Carolina writes: "I've been working through your "Introducing EJB-CMP/CMR" tutorials. Great stuff. Well presented - simple and straight forward. Really learning a lot. " Patrick from the U.S.A. writes: "Great Job on part 1 and 2 of your tutorial on CMP/CMR and EJB QL. When will part 3 and 4 be out.? Will it be able to run on JBoss Resin, and Orion." (It is done! It should be out soon, I am working on getting the example to work with Resin, JBoss. Part 3 and 4 works with WebLogic.--Rick)
Another resource is the Developer's guide to understanding EJB.... Developer's guide to understanding EJB Here is what people think of it... "You can either read the [Sun Microsystems Enterprise JavaBeans] spec, or the Developer's Guide to Understanding EJB. For developer's new to EJB, you should begin with the great primer, and VisualAge for Java" - IBM Toronto Labs In general check out IBM developerWorks.... they have a lot of really good Java tutorials as well... IBM Java tutorials One good thing about the IBM tutorials is that they offer them in PDF format as well as HTML. PDF is nice so you can print out the tutorial and read it offline.