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.
Gump provides large scale continuous integration for various open source projects.
Apache Etch provides is a cross-platform, language- and transport-independent RPC-like messaging framework.
Etch is a cross-platform, language- and transport-independent framework for building and consuming network services. The Etch toolset includes a network service description language, a compiler, and binding libraries for a variety of programming languages. Etch is also transport-independent, allowing for a variety of different transports to be used based on need and circumstance. The goal of Etch is to make it simple to define small, focused services that can be easily accessed, combined, and deployed in a similar manner. With Etch, service development and consumption becomes no more difficult than library development and consumption.
Java-based build tool
Apache Ant is a Java-based build tool.