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 Commons Net
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.
Apache HBase software is the Hadoop database. Think of it as a distributed, scalable, big data store.
Use Apache HBase software when you need random, realtime read/write access to your Big Data. This project's goal is the hosting of very large tables -- billions of rows X millions of columns -- atop clusters of commodity hardware. HBase is an open-source, distributed, versioned, column-oriented store modeled after Google's Bigtable: A Distributed Storage System for Structured Data by Chang et al. Just as Bigtable leverages the distributed data storage provided by the Google File System, HBase provides Bigtable-like capabilities on top of Hadoop and HDFS.