Xelem
- A compact Java-library to read and write Excel files of type SpreadsheetML. [Open source, GPL]
- http://xelem.sourceforge.net/

PowerML
- A product suite for Java and XML based, platform independent managing Microsoft PowerPoint presentations. [Commercial]
- http://www.powerml.com

Jackcess
- Pure Java library for reading and writing MS Access databases. [Open source, LGPL]
- http://jackcess.sourceforge.net/

Java Excel API
- Class library for read/write and modify Excel 95, 97, 2000 spreadsheets. [Open Source, LGPL]
- http://www.andykhan.com/jexcelapi/

ExtenXLS Java/Excel Toolkit
- Dynamic Excel reporting in their Java web applications. [Commercial]
- http://www.extentech.com/estore/product_detail.jsp?product_group_id=1

Outlook PST to Unix mail box converter
- Converts .pst mail files to unix mbox files. [GPL]
- http://sourceforge.net/projects/ol2mbox

Davisor Offisor
- A XML/SAX -compliant 100% pure Java Microsoft Word document content parser, with easy DOM/XSLT integration. Exposes also document structure, style information, and even graphics. [Commercial, demos]
- http://www.davisor.com/offisor/index.html

POI
- APIs for manipulating various file formats based upon Microsoft's OLE 2 Compound Document format using pure Java. Most MS Office files use OLE2CDF. [Open Source, BSD-like]
- http://jakarta.apache.org/poi/index.html