I know Pixia ( http://park18.wakwak.com/~pixia/
) has been mentioned before. Just wanted to point out that version 4 came out in English a few months ago.
Pixia is a nice enough freeware program for drawing and painting and it has one feature that I absolutely love: excellent line smoothing. This is something that's right up at the top (together with more advanced brush settings) of my wishlist of things to be implemented in Photoshop. With a bit of practice you can get very nice smooth lines even with a mouse using Pixia. I haven't done much in the way of line art lately, but awhile back I regularly sketched in Photoshop and then went over to Pixia for inking.