The ASF @ 15 - The Apache Software Foundation Celebrates 15 Years of Open Source Innovation and Community Leadership http://s.apache.org/wZr
... and cheered at ApacheCon Europe http://s.apache.org/1o4
The ASF is made up of more than 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.
BeanUtils provides an easy-to-use but flexible wrapper around reflection and introspection.
Apache Tez is an effort to develop a generic application framework which can be used to process arbitrarily complex directed-acyclic graphs (DAGs) of data-processing tasks and also a re-usable set of data-processing primitives which can be used by other projects.
An open-source, office-document productivity suite
Apache OpenOffice is an open-source, office-document productivity suite providing six productivity applications based around the OpenDocument Format (ODF). OpenOffice is released on multiple platforms and in dozens of languages.