Hallo,
here some Links for 3D file browser:
Cad Preview Image for Rhino files in the windows explorer: a free DL
http://www.lynx4d.com/products.php
This one is free in a light version until April, 15 2006. Better download it now. 
Together with the 3dm CAD preview image tool, it show 3dm & 3ds & obj files.
http://www.mootools.com/plugins/us/index.asp
…this program P3DO Explorer pro 3D browser and Image viewer is a shareware, and it’s currently at V1.8. It’s a file browser/viewer, the website says April 06 will be a 2.0 release with 3ds viewing. This tool dosn’t show 3dm files, but it handle zipped 3d files.