DeviantArt - deviantART was created to entertain, inspire, and empower the artist in all of us.
Sketchboard.io - Visual Remote Teamwork. Solve problems and create ideas on endless whiteboard with your teammates by sketching.
Brush Ninja - Hand-drawn Animated Gif Creator
Draw.Chat - Anonymous real-time whiteboard with text and video chat.
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.
MultiDraw - Draw with others in real time.