Books
Content Design by Sarah Richards
The Elements of Content Strategy, by Erin Kissane
Plain Words, by Gowers and Fraser
Content Strategy for Web, by Kristina Halvorson
Letting Go of the Words, Writing Web Content that Works, by Janice Redish
Transform, by Gerry McGovern
Forms that Work by Caroline Jarrett
Some other style guides we like
Other resources
Content collections
Content Strategy Resources from Qordoba