Resources about Writing and Internet Etiquette
RFC 1855 about Internet Etiquette
The Net: User Guidelines and Netiquette
by Arlene H. Rinaldi
The Core Rules of Netiquette
excerpted from the book
Netiquette
by Virginia Shea.
Link collection compiled by the Onalaska, WA School district
Very good, unfortunately in German, etiquette not only for email but also usenet groups.
Configuring Mail Clients to Send Plain ASCII Text
University of Utah Writing Center