"Apache Geronimo is the new kid on the Java Platform, Enterprise
Edition (Java EE) server block (version 1.0 was released in January
2006). It's a powerful combination of several other projects,
including OpenEJB, Axis, Jetty, Tomcat, ActiveMQ, and ServiceMix.
Geronimo is making headlines these days, because it's a different
kind of Java 2 Platform, Enterprise Edition (J2EE)-certified
server. It's built from the ground up using a dependency injection
container. Geronimo also provides fine-grained control over class
loaders, allowing you to specify parent-child relationships instead
of just dropping all your classes inside a shared lib directory and
hoping for the best.
"Apache Pluto is the reference implementation for the Portlet
specification. It isn't a full-fledged portal server itself..."