OpenEJB is a simple, lightweight Enterprise JavaBeans (EJB) container and server. You can embed OpenEJB in your own applications, or in a Web application server like Tomcat, or run it as a standalone EJB server. It supports EJB 3.0, 2.1, 2.0, and 1.1, and has partial support for EJB 3.1.
EJOE is a lightweight Java remoting framework built to send and receive objects through pluggable (de)serialization mechanisms. It offers a high-performance, simple, and clean object request broker (whereby ORB is meant in its natural manner and not in its relation with CORBA), with server and client components for your client/server applications. It's a highly scalable implementation of the common request-process-response pattern based on Java NIO. It does support optional remote class loading to avoid redundant classpath entries, but doesn't require stubs and/or proxy objects.
Apache ActiveMQ is a popular and powerful message broker and enterprise integration patterns provider. Apache ActiveMQ is fast, supports many cross language clients and protocols, comes with easy-to-use enterprise integration patterns and many advanced features, while fully supporting JMS 1.1 and J2EE 1.4.
The gLite distribution is an integrated set of components designed to enable resource sharing. In other words, this is middleware for building a grid. The gLite middleware is produced by the EGEE project. The distribution model is to construct different services ("node-types") from these components and then ensure easy installation and configuration on the chosen platforms.