Witeboard - A real-time whiteboard for your team. No signups required.
Mural - MURAL is a visual collaboration workspace for modern teams.
Whiteboard Fox - Simple Online Whiteboard
Sketchboard.io - Visual Remote Teamwork. Solve problems and create ideas on endless whiteboard with your teammates by sketching.
Stormboard - Stormboard empowers data-driven companies to turn their unstructured whiteboards into data-rich collaborative workspaces; enabling data-driven decisions and efficient processes — often eliminating the need for meetings entirely.
BeeCanvas - Realtime & Interactive Whiteboard. Collect and organize everything in one place.