According to Google, SketchUp is a
"powerful yet easy-to-learn 3D software tool that combines a simple, yet robust tool-set with an intelligent drawing system that streamlines and simplifies 3D design. From simple to complex, conceptual to realistic ..."In addition, under Audio category, Audacity is a free, easy-to-use audio editor and recorder for Windows, Mac OS X, GNU/Linux, and other operating systems. Audacity is extremely popular application for podcasters. For a full list of feature, see here.
SketchUp and Audacity are completely free.