Bibus is a bibliographic database. It uses a MySQL or SQLite database to store references. It can directly insert references in OpenOffice.org and MS Word and generate the bibliographic index.
IAwiki is a collaborative knowledge base for the topic of InformationArchitecture. Anyone can contribute, and there are no pre-registration hoops to jump thru ... just click the "Edit This Page" link at the bottom of any page.
Open source graph visualization software. Takes descriptions of graphs in a simple text language, makes diagrams formatted as images, SVG for web, PS for PDF, GXL (XML dialect), and more.