First I’d like to say, I’m not a fan of AutoCad. Second I’d like to say I’m a fan of AutoDesk draw for the web. http://draw.labs.autodesk.com/ This allows you to draw in 2D on any of the standard web browsers (IE, Firefox, others). With out any downloads, installs etc. You can take this offline if you have Google Gears installed, which is a platform for taking web applications offline. You can save the files on their servers or your own. No signup just start drawing. Check it out.