I've been looking for some online drawing tools so that if I want to make a quick sketch I don't have to photoshop every time. Here's what I've found.
http://www.zefrank.com/scribbler/
turns a simple line drawing into a detailed generated picture, ala Harmony.
http://mrdoob.com/projects/harmony/
Kinda hard to explain- like scribbler except the fuzziness and generative part happens as you draw.
http://www.jacksonpollock.org/
Sling paint like Jackson Pollock. Click to change the pain color.
http://www.queeky.com/app, http://www.sumopaint.com/app/,
When you don't wanna fire up photoshop, these are some pretty good online alternatives.