Adobe has released Adobe Acrobat3D for easing collaboration when working with 3D (CAD) data. The gist of it is you get a PDF with an interactive 3D data viewer (rotate, zoom, etc). Pretty cool stuff. It currently seems to be aimed at the manufacturing sector, but I hope that at some point it becomes a standard export format for a number of design/modeling applications, as it would make the proofing/review process so much easier when dealing with clients.
View a sample file with embedded 3D (PDF: 2.8M)
More info at the Adobe site.