The Open Data Movement aims at making data freely available to everyone. The goal of the Linking Open Data project is to make various open data sources available on the Web as RDF and to set RDF links between data items from different data sources. The project's progress is documented on their wiki, and the work is coordinated through a mailing list.
The FOAF whitelisting project proposes the creation of a FOAF and trust metric based system to whitelist email coming from trusted senders and integrate the system into spamfighting tools, MTAs and MUAs. The project seeks to use the vast social networks already encoded in FOAF to find if someone you know knows the sender of the e-mail just received on your mail server. The foaf-dev mailing list is used for development.
The Knowee project aims at a distributed, web-based contact organizer. It should be largely bootstrapped via the XFN and hCard microformats, but uses SPARQL (or maybe just a simple RDF lib) for application functionality and RDF for information integration. The project has a Google code page.
The POWDER browser extension focuses on the work of the POWDER working group and builds on work on Segala's Search Thresher for Firefox. The aim of this project is to create a browser extension which allows the user (1) to detect POWDER and allow the user to filter content based on their preferences and (2) to allow users to make POWDER statements relating to a specific website.