DrawPile - Drawpile is a drawing program that lets you share the canvas with other users in real time.
Limnu - Sketch, share and collaborate with your team
Aggie.io - Draw a picture together with your friends in real-time over the internet in your browser.
Draw.Chat - Anonymous real-time whiteboard with text and video chat.
Formgraph - Formgraph is a collaborative vector drawing tool and social network.
Sketchboard.io - Visual Remote Teamwork. Solve problems and create ideas on endless whiteboard with your teammates by sketching.