PBS Learning Media has short videos and other resources specifically designed for use by educators that are drawn from PBS programs. Registering on the site and using the materials is free. In addition, they have relatively inexpensive professional development programs for teachers, including self-paced online classes.
With more than 30,000 artworks available from 151 museums around the world, the Google Art Project is a treasure trove for educators. The site lets you link directly to works of art that students can see in high resolution detail, along with helpful notes about the artist, the artwork, its location, dimensions and more.