I think it is important that shy students feel like there is a community in their classroom. This activity book is prefect for bullying prevention. These interactive lessons can be used in small group sessions and can foster a more welcoming classroom.
Quiet Revolution is a powerful resource for teachers. I like that parents posts about their experiences in the education system with introverted children. This site acts as a learning curve for every teacher wanting to best serve his/her student.
Susan Cain's, Quiet: The Power of Introverts in a World that Can't Stop Talking is a must-read for every teacher. This books provides a broader understanding of introverts and how they adapt to the world. It provides helpful insights whether you're an introvert yourself, or work in a classroom with introverted students.