DWG and DXF - AutoCAD files
SketchUp can import DXF and DWG files - with a free trial period
DraftSight lets you view and edit DWG files.
eDrawings Viewer from SolidWorks Can view DWG and DXF files
Microspot DWG Viewer can open DWG files.
QCad is a cross platform and also for macOS.