I found this program just five minutes ago and I think it is very interesting, especially for those of you who like CAD design. If you are interested you can watch the on-line demonstration here.
This program is not free but there is a 30-day trial version. The new version brings many useful improvements: completely new tools for 3D shells, 3D pipelines and 3D wires, a substantially improved 3D editing function allowing more complex editing, significantly improved STEP file import, new 3D checking functions, an extended tutorial and quick demonstration with new Flash examples. - etc.