I've written a number of EJB articles for the IBM VisualAge Developer's Domain Technical Journal and DeveloperWorks.
One ongoing project is a series of articles with Scott Rich from the VisualAge for Java development organization on the support for EJB's in VisualAge for Java 3.0. The goal of the series is to cover the support for implementing OO designs in EJB's using VAJ.
The articles so far are:
http://www7.software.ibm.com/vad.nsf/Data/Document2616?openDocument&p=1&BCT=3&Footer=1
http://www7.software.ibm.com/vad.nsf/data/document2310?openDocument&p=1&BCT=1&Footer=1
http://www7.software.ibm.com/vad.nsf/Data/Document2316?openDocument&p=1&BCT=1&Footer=1
http://www7.software.ibm.com/vad.nsf/Data/Document2330?openDocument&p=1&BCT=1&Footer=1
http://www7.software.ibm.com/vad.nsf/Data/Document2341?openDocument&p=1&BCT=1&Footer=1
The DeveloperWorks Article is on Why you would or would not want to use EJB's.
http://www-4.ibm.com/software/developer/library/ibm-ejb/
See: EjbArticles