The GNOME Documentation Project Web page lists current GDP projects and members.

The GNOME Documentation Style Guide is a guide to how a document should be structured, written, and proofread.

Norman Walsh's DocBook: The Definitive Guide in an excellent book on DocBook, available both online and in print.

Dave Pawson's DocBook Frequently Asked Questions is a good source for information about writing in DocBook, tools for DocBook, and stylesheet customizations.