http://smarthistory.khanacademy.org/ – an excellent Art history site provided by Khan Academy.
http://www.escapemotions.com/experiments/flame/index.html#top – Flame painter – a beautiful bit of fun.
http://www.virtualdali.com/ – A website showcasing the work of Dali
https://wbx-files.s3.amazonaws.com/jacksonpollock_by_miltos_manetas.swf – create your own Jackson Pollock, without the mess.
Many, many art things.
Art lessons plans and resources.