The site is American but the resources are universal. Since 1996 Incredible @rt Department has been aggregating visual arts lesson plans, activities, toolboxes and galleries from kindergarten to university picking up a brace of arts and learning awards from then to 2012.
The categories flow along lessons, references, toolboxes, links to recommended sites, a dedicated section to cartooning, activities and games, zines, blogs, forums, podcasts, student galleries and a section called Art Rooms where teachers in America and from Australia open up their rooms to display works and describe their practices and techniques. As much as the site is updated it also keeps archives dating back to its beginnings.