The following images were painted on my Nintendo DS.
Not too long ago I installed Colors! a free digital painting program onto my DS and I have to say it is pretty awesome. It's a bare bones program, no layers, no adjustments, not even undo - so to that affect, it emulates traditional painting a little bit more than Photoshop. You are limited by how small the DS screen is which makes it a little hard to draw, but its really fun sketching with a stylus directly onto a screen. Consider it a $150 dollar cintiq that you can take with you anywhere. I recommend it to everyone interested in digital painting.
These are all really quick sketches. My biggest goal these days is to work on incorporating saturated colors into my work... and these are a little more saturated than I expected them to be but I guess that means they are a success.
If you own a DS, or want to look into this more, checkout this URL: Colors! - Setup Tutorial