The Sun's web site has several levels of documentation, starting from simple tutorial. There is an on line book by Ed Roman, it is also available as hard copy. The serverside.com is a good place to look for design patterns and other design related aspects of using EJB. Malleka
The "Core J2EE Patterns" (SUN) will definitively help you.
/ JeanLouis<br /><i>"software development has been, is, and will remain fundamentally hard" (Grady Booch)</i><br /> <br />Take a look at <a href="http://www.epfwiki.net/wikis/openup/" target="_blank" rel="nofollow">Agile OpenUP</a> in the Eclipse community