Check with your local school librarian for eBooks, databases, books and other resources you and your students will find useful.
Library of Congress: Teaching With Primary Sources is an excellent site for primary sources, as well as lesson plans.
History Unbound - Links to Primary Sources and Assessments
Teaching about the Holocaust? Echoes and Reflections has professional development and educational materials for Middle and High School teachers. They offer webinars, online and in-person classes as well.