PaintBerri - PaintBerri is a free art site that offers an awesome oekaki community.
DeviantArt - deviantART was created to entertain, inspire, and empower the artist in all of us.
okekai - A small community site where you can draw, animate, and chat through pictures all for free
pixiv - pixiv is an illustration community service where you can post and enjoy creative work. A large variety of work is uploaded, and user-organized contests are frequently held as well.
Brush Ninja - Hand-drawn Animated Gif Creator
RateMyDrawings - RateMyDrawings is an online drawing community that allows artists and illustrators to draw online.