Aigaion is a freeware bibliography system that I am developing together with some friends. It is web-based (PHP/MySQL) and has multi-user support. It was build on the BibTeX format, but supports other formats as well. Some of the key features are:

• Extensive support for organizing a bibliography in a topic structure
• Personal and public annotations on each publication
• Multi-user support
• Easy Im- and Export
• Intuitive user interface

For more information on Aigaion, please visit aigaion.nl or aigaion.sourceforge.net.