The ASF is made up of over 100 top level projects that 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.
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. Use for prototyping or production.
Apache Axiom is an XML object model supporting deferred parsing.
Apache Axiom is a StAX-based, XML Infoset compliant object model which supports on-demand building of the object tree. It supports a novel "pull-through" model which allows one to turn off the tree building and directly access the underlying pull event stream. It also has built in support for XML Optimized Packaging (XOP) and MTOM, the combination of which allows XML to carry binary data efficiently and in a transparent manner. The combination of these is an easy to use API with a very high performant architecture!
Gump provides large scale continuous integration for various open source projects.