Here is a complement for Freewheel that only handles DWF files at this point. At SolidWorks Labs there is Drawings Now a simple web viewer that can read DWG, DXF or native SolidWorks drawing files. Besides is a sample drawing in DWG 2007 format that I tried. A nice thing is that it remembers the drawings I have uploaded so I easily can view them again.
DWG navigator is a cool viewer (Vista look without Vista) that is built using Microsoft Visual Studio 2005, WinFX, Expression and .NET Framework 3.0. If Visual Studio really needs to be installed as it says I don't know since I did have everything installed already. It can search within files, find where for example an xref is used, run Pack and Go, save to newer or older file versions, rename a DWG file and update the references where it is used, replace a file with another one and have the host file updated, etc. Quite many functions and much more than a viewer. (For some reasons lmutil.exe v. 11.3 is included in the install folder. Will it be licensed using FLEXnet later on and have a price tag on it? There is 87 days remaining on the beta as well the about dialog box says.)