This post is an excerpt from Free Technology for Teachers: 11 Art & Music Resources to Try in 2011.
The Museum of Modern Art offers a sizable collection of online resources for teaching art lessons. Part of that collection is a series of lesson plans, but there are also collections of art for students, an art game for young (5-8 years old) students, interactive activities for older students, and podcasts about art and artists. The MOMA lesson plans collection can be searched by theme, artist, medium, or subject. If the lesson plans in the collection don't offer quite what you're looking for, MOMA has free resources you can use in developing your own plans. MOMA offers many images and PDFs that you can use in developing own lessons and or slideshows.