Autodesk Design Review - Design Review lets you view, mark up, print, and track changes to 2D and 3D files.
Free DWG Viewer - Free Viewer for DWG, DXF, DWF View AutoCAD DWG/DWF/DXF files View & measure DWG, DXF, DWF
LiteCAD - Create, edit, view, and print 2D CAD drawings using the file formats: dxf, dwg, shp ;Download-Size...
ODA Viewer - ODA Viewer is a web-based software solution that allows you to view the files based on ODA format and you can easily zoom the file for detail visualization.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer
Amethyst CADwizz Ultra - Amethyst CADwizz Ultra is an AutoCAD viewer software solution that allows you to view the files which are created by AutoCAD software and you can even view the files without the presence of AutoCAD.