DWGSee is a CAD file viewer for Windows that stands out for its simplicity and ease of use, yet still has the capability to allow you to take notes and highlight any section of the display that you want.
It has a clear, simple interface with a large viewing area that takes up most of the screen, and a small toolbar. There is a tab manager so that you can navigate between various files with no delay, and it supports layers so that you can choose a specific layer to view.
Once you add support for AutoCAD 2008 files to the mix, you can't deny that DWGSee is a great CAD file viewing program.
Support for AutoCAD 2008.