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.
Commons Betwixt: mapping beans to XML
Apache Deltacloud provides common front-end APIs to abstract differences between cloud providers.
Deltacloud contains a cloud abstraction API - whether the Deltacloud classic API, the DMTF CIMI API or even the EC2 API. Each abstraction API works as a wrapper around a large number of clouds, shielding users from their differences. For every cloud provider there is a driver "speaking" that cloud provider's native API, freeing you from dealing with the particulars of each cloud's API.
Java API To Access Microsoft Document File Formats
APIs for manipulating various file formats based upon Open Office XML (ECMA-376) and Microsoft's OLE 2 Compound Document formats using pure Java. Apache POI is your Java Excel, Word and PowerPoint solution. We have a complete API for porting other OOXML and OLE 2 Compound Document formats and welcome others to participate.