The ASF is made up of nearly 150 top level projects which cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.
ActiveMQ is the most popular and powerful open source Message Broker.
ActiveMQ is a fast and powerful Message Broker which supports many Cross Language Clients and Protocols and many advanced features while fully supporting JMS 1.1 and J2EE 1.4.
Apache Isis is a framework for rapidly developing domain-driven apps in Java
Apache Isis is a framework for rapidly developing domain-driven apps in Java. Write your business logic in entities, domain services and repositories, and the framework dynamically (at runtime) generates a representation of that domain model as a webapp or as a RESTful API. For prototyping or production.
Java-based template engine
Velocity is a Java-based template engine. It permits anyone to use a simple yet powerful template language to reference objects defined in Java code. When Velocity is used for web development, Web designers can work in parallel with Java programmers to develop web sites according to the Model-View-Controller (MVC) model, meaning that web page designers can focus solely on creating a site that looks good, and programmers can focus solely on writing top-notch code. Velocity separates Java code from the web pages, making the web site more maintainable over its lifespan and providing a viable alternative to Java Server Pages...