Project Butterfly is an Autodesk Technology Preview that enables AutoCAD® users to edit and collaborate on AutoCAD drawings through a Web browser. With Project Butterfly, AutoCAD users can share and work on DWG^TM files with colleagues and clients from any computer with an Internet connection.

• Share drawings with other people. View and edit DWGs without downloading any software, using just a Web browser.

• Invite your project team to an online meeting where all sides can discuss and co-edit a drawing in real-time. Or browse through comments and changes on your own time.

• Use Project Butterfly to collaborate with colleagues and clients. Anyone can access Project Butterfly, even if they don't have AutoCAD installed, and even if they don’t have a Project Butterfly account.
  http://labs.autodesk.com/technologies/butterfly/