YouWHO is an Open Source Java web-application for managing information on people and organisations your business deals with everyday. YouWHO has a very powerful relational database engine that ensures that a person's contact details are always correct even in very dynamic environments.
YouWHO supports traditional and electronic bulk mailouts through sophisticated group functionality. Data within YouWHO is very flexible and can be exported to PDF, HTML, CSV, VCard and XML formats. The application binaries and source can be downloaded from the Subversion repository.
A tarball of the latest stable release is available here or you can browse the source tree.
Screenshots:
Logon Screen 
Advanced Search 
People Information 
Organisation Information 
Save & Export Options 
PDF Output