Autodesk® DWG TrueView™
"You can view .dwg files with Autodesk® DWG TrueView™ software, a free* stand-alone .dwg viewer with DWG TrueConvert™ software included. Built on the same viewing engine as AutoCAD® software, DWG TrueView enables you to view .dwg and DXF™ files, just as you would in AutoCAD."

Adobe® Acrobat® Reader®
"Adobe® Reader® is free software that lets you open, view, search, digitally sign, verify, and print PDF files."

Autodesk® Design Review
"Accelerate your design reviews on your desktop with Autodesk® Design Review software. It’s the free*, all-digital way to view, mark up, print, and track changes to Autodesk 2D and 3D files—without the original design software. Work with a wide variety of file formats, including DWF™ and DWFx, DWG™ and DXF™ (requires installation of free DWG TrueView™ software) and Adobe PDF, as well as several image file types."

DWGicon.dll
"DWGicon.dll is a Windows shell extension that enables you to identify the version of a drawing just by looking at its icon in explorer. You don't need to have CAD software installed on your machine for it to work."

ExpressView Browser Plug-in (MrSID)
"The ExpressView Browser Plug-in (formerly the MrSID Browser Plug-in) gives you the ability to view MrSID and JPEG 2000 images natively in standard Windows Web browsers. The intuitive graphic user interface allows you to view, magnify, measure, print and save images. The ExpressView Browser Plug-in is free for individual use and is easily installed as a plug-in for Internet Explorer and Firefox Web browsers."

ESRI ArcReader (ArcGIS Desktop Viewer)
"ArcReader is a free, easy-to-use desktop mapping application that allows users to view, explore, and print maps and globes. Anyone with ArcReader can view high-quality interactive maps authored by a high-level ArcGIS for Desktop product and published with the ArcGIS Publisher extension."

ArcGIS Explorer Desktop (GIS Data Viewer)
"ArcGIS® Explorer offers an easy way to view, share, and present your authoritative geographic information system (GIS) data. It’s a free GIS viewer that connects directly to a variety of ready-to-use ArcGIS® Online basemaps and layers and enables you to add your own map services or local data."

Google Earth
"Google Earth allows you to travel the world through a virtual globe and view satellite imagery, maps, terrain, 3D buildings, and much more. With Google Earth's rich, geographical content, you are able to experience a more realistic view of the world. You can fly to your favorite place, search for businesses and even navigate through directions."

Visio 2010 Viewer
"Microsoft Visio 2010 Viewer allows anyone to view Visio drawings and diagrams (created with Visio 5.0 through Visio 2010) inside their Microsoft Internet Explorer (versions 5 through 8) Web browser."