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.
Forge software for hosting software projects
Apache Allura is an open source implementation of a software "forge", a web site that manages source code repositories, bug reports, discussions, wiki pages, blogs and more for any number of individual projects.
Perl API to the Apache Xerces XML parser.
XML::Xerces is the Perl API to the Apache project's Xerces XML parser. It is implemented using the Xerces C++ API, and it provides access to most of the C++ API from Perl. Because it is based on Xerces-C, XML::Xerces provides a validating XML parser that makes it easy to give your application the ability to read and write XML data. Classes are provided for parsing, generating, manipulating, and validating XML documents. XML::Xerces is faithful to the XML 1.0 and 1.1 recommendations and associated standards (DOM levels 1, 2, and 3, SAX 1 and 2, Namespaces, and W3C XML Schema)....
Apache Phoenix takes a NoSQL key/value store such as Apache HBase and turns it into a SQL database.
Apache Phoenix is a SQL query engine for accessing NoSQL datastores such as Apache HBase. It is accessed as a JDBC driver and enables querying, updating, and managing NoSQL tables through standard SQL. Instead of using map-reduce, Apache Phoenix compiles your SQL query into a series of HBase scans and orchestrates the running of those scans to produce regular JDBC result sets. Direct use of the HBase API, along with coprocessors and custom filters, results in performance on the order of milliseconds for small queries, or seconds for tens of millions of rows.