Another CAD program to consider is Rhino. It has an academic version at low cost as well, but it doesn't cut you off after a year like Solidworks does. (Note, I'm a long time SW user and love it, but it was out of my price range and I had already used my academic version up). Rhino is not a parametric modeler like SW or inventor, but it gets the job done and gives you a little more flexibility with organic shapes. Just something else to consider...