A few great websites I have found:
sketch & Paint program http://www.onemotion.com/flash/sketch-paint/
Pencil Madness: http://pencilmadness.com/pencil_madness
Pixel Art: http://piq.codeus.net/
This week I let the students work with different drawing apps on android tablets and iPod/iPhones. As well as a group painting project on the smartboard using the website program http://www.onemotion.com/flash/sketch-paint/