Project Draw

"Project Draw is a new feature-rich web-based vector drawing application built by the Labs team. Use it to create simple floor plans, electronic-circuit diagrams, network diagrams, user interface mock-ups, and more. Save your work in a variety of formats on our server or yours. No plug-ins or downloads required - if you have a JavaScript-enabled Internet Explorer or Firefox browser, you’re good to go. If you've registered with Autodesk Labs, logon and try Project Draw out now!"

http://draw.labs.autodesk.com/ADDraw/draw.html