Cheap 3D software Package, that will allow me to machine .stl or.iges files?

[JAZZCNC]

do you know of any free 3D software that may be available?

Here you go used with with Gmax software which is free (or used to be.!).! Very powerful software But I warn you it's very steep learning curve and not recommended for first timers.

http://www.cnc-toolkit.com/index.html