Parallax Press
Publishes books by Thich Nhat Hanh and others. From the website - "Parallax Press is a project of the Community of Mindful Living, dedicated to publishing books and tapes on socially engaged Buddhism."
Shambhala Publications
Books on Buddhism. A wide diversity of works.
Tharpa Publications
Publisher of Buddhist books by Geshe Kelsang Gyatso about basic Buddhism, meditation and the Mahayana and Vajrayana paths.