Go Geronimo Go!
Geronimo 1.0 was released last week. Apache Geronimo is a new, open source, J2EE 1.4 certified application server. It is built from many established open source projects, like OpenEJB, Tomcat and the Derby database so it already has some pedigree.
The more I think about it, Java developers are in a great position. There is a great choice of open source J2EE app servers, Geronimo, Jonas, JBoss, Glassfish or you get free access to many commercial servers.
If you are interested in trying out Geronimo with the addition of mysql and postgresql in a sandboxed environment that won't overwrite your existing app, I've written up some notes to get started with our preview of Geronimo 1.0. The download and instructions are available here