I think I'm going to take it down soon, but for a work/training project I made a prototype database thing for pd that documents external objects w/brief descriptions about what they do, tags, and long description/documentation. Users could edit descriptions, docs, and tags of objects and libraries as well as search object or libraries by name, tag, or author.
http://puredatabase2-app-bucket.s3-website-us-west-1.amazonaws.com

I guess it's not really a wiki but.. I thought such a database/wiki thing might also be useful