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.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
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.
FreeCAD - An open-source parametric 3D modeler
K-Display View - K-Display View is a desktop-based software that enables you to view the drawings and it allows you to give access to your team members so that everyone can participate in a project in a better way.
SketchUp - 3D for Everyone