The best free 3D CAD software (with surface modeling) is VX Modeler (
www.vx.com/VX_Modeler.cfm ). It is usually a $1200 package but if you attend their free seminar, they give you one seat per company (or individual) for free, it is FULLY FUNCTIONAL and DOES NOT EXPIRE!
I drove 30 minutes to their Anaheim California seminar and I didn't pay a cent for their modeler software. Zero pressure seminar. They basically show off their software and hope you like it enough to buy extra seats for your company.
See
www.vx.com/seminars.cfm for their seminar schedule. They are pretty much inactive in the USA for the holiday season but will pick up after the New Year. You can call them and request for a seminar in your area.
Also try a nice free CAD package (without surface modeling) :
http://www.alibre.com/xpress/softwar...ign-xpress.asp