Wikipedia
ShareCAD
ShareCAD or ShareCAD.org is a free online service aimed at viewing different DWG and CAD formats as well as 3D models in a web browser. The service doesn’t require any installation or registration and enables users to view vector, raster and 3D formats online. ShareCAD also offers its users a free iframe plugin for viewing DWG at a site.
The service runs in web browsers powered by Windows, OS X, Linux, Android, iOS and Windows Phone and is available in the following languages: English, German, French, Italian, Spanish, Portuguese and Russian.