A good place to start fro free cad is: http://www.123dapp.com/
There are numerous cad packages from autodesk - all free.

Also depending on the way your brain works openscad: www.openscad.org
Is awesome :-)

Slicer wise the main three would be: cura, slic3r and simplify3d - simplify3d is the only one you pay for the other two are free.

What we find is that commercial cad people are only really happy with commercial software and almost everyone else manages very nicely with the free stuff :-)
On the grounds: what you never had - you don't miss.