One situation that often happens is that customers want to see your 3D work. Often, they just get a 2D drawing and dont get to see the beauty that is the 3D Model. Each CAD package usually offers some sort of native viewer to view native CAD files. Without that viewer, it would be alomst impossible for someone without CAD to view them---almost...
I have offer a service called GrabCad to all of my customers to be able to view, comment on, and measure their CAD files. The CAD files are synced daily with GrabCad which allows the customer to view the latest revision(s). They are able to spin their models around and actually see what I see when I model them. Files are also backed up on here as well as in my Dropbox. I can go back revisions as necessary as well.
Basically, GrabCad is my PDM software (Product Date Management). It works well, and best of all, its FREE.