I have been a SolidWorks user and fan for many years. In my build thread DoctorZ mentioned this new software, developed by the original founders of SolidWorks.
https://cad.onshape.com
This is worth signing up for! It's fully functional and is FREE under a few conditions. Parametric modeling takes a little getting used to, but once you have learned to model in this way you can never go back to surface modelers like SketchUp or Rhino for designing parts that need to fit together.
This is a marketing quote...
"Onshape is a new venture-backed company that is applying cloud, web and mobile technologies to CAD. Our team includes the original SolidWorks team plus elite engineers from the data center, security, and mobile industries. We are working hard on a new generation of CAD. It's not quite ready yet"
I signed up today for the "Free" version and amazed this software works, so well in a modern browser like Chrome...
https://www.onshape.com/tutorials
More marketing info
http://www.solidsmack.com/cad/onshape-developing-new-cad-system-five-reasons-just-beginning/

3D Parametric Solid Modeling Software "FREE"
Web based, SolidWorks style "FREE" software