Google is now able to index certain 3D file formats. These file formats include: - filetyp:dwg for AutoCAD files - Google even parses the file and gives descriptions derived from the content! - filetype:3ds for 3D-Studio files - again, then content is parsed - filetype:c4d gives you Cinema 4D files - but no content parsed - filetype:lwo finds LightWave files with descriptions - filetype:obj well, you have to hand-pick the 3D files from many non-3D-results...
A thread at WebmasterWorld named Google filetype goes 3D! discusses this topic. The thread then delves into how well Google does this. Answer is, not all that well, in terms of relevancy.