MusicBrainz  
   Downloadable song metadata--artist/album/track information--for audio CD and MP3 music players (Open Content License).
   http://www.musicbrainz.org

Technomanifestos Network  
   Collaborative resource on the history of computing and the Internet (GNU Free Documentation License), and the online companion to the book Technomanifestos.
   http://www.technomanifestos.net

PlanetMath  
   Collaborative, peer-reviewed mathematics encyclopedia with TeX input, inspired by MathWorld (GNU Free Documentation License).
   http://www.planetmath.org

Connected: An Internet Encyclopedia  
   The engineering, theoretical concepts, and organizations of the Internet (freely distributable).
   http://www.freesoft.org/CIE/

Open Site  
   A volunteer-run open content encyclopedia.
   http://open-site.org/

Metaweb  
   A project initiated by author Neal Stephenson as a resource first to annotate his novel Quicksilver, but based on the broader concept of a "metaweb" devised by Danny Hillis.
   http://www.metaweb.com/

Disinfopedia  
   Directory of public relations firms, think tanks, industry-funded organizations, and industry-friendly experts that work to influence public opinion and public policy on behalf of corporations, governments and special interests.
   http://www.disinfopedia.org/

Wikipedia Article - Nupedia  
   Nupedia was a public peer-reviewed general encyclopedia created by volunteer scholars, with resources for readers and contributors (GNU Free Documentation License). It can be considered to be Wikipedia's direct ancestor.
   http://en.wikipedia.org/wiki/Nupedia