Free J2EE 1.4 stack: JOnAS 4.1
I saw this link on another Java blog. The ObjectWeb software is high quality stuff: I frequently use their Joram JMS software for guaranteed asynchronous messaging.
A little too bad that I have been moving away from using EJBs in the last year or so - most of my web app projects are small to medium sized projects where it usually makes sense to just use a JSP container, and use: JDO (Hibernate), hand written JDBC, or something like Prevayler.
Still, for large projects, the full J2EE 1.4 stack rocks.