I've been looking for a while and haven't been able to find anything in the league of Inventor or Solid Works. There are a couple of useful if not fully featured programs around.
These is no shortage of 3D Kernels, ACIS, Parasolid and OpenCascade are all available but no one as yet seems to have launched a main stream general purpose 3D CAD package for Linux. I hope it'll only be a matter of time as I'd like to move away from Windows completely is at all possible.