I recall various posts about this type of software over the years. Very few <img src=/S/free.gif border=0 alt=free width=30 height=15> offerings available, but this one is. The sample gallery looks quite impressive too.

"Envisioneer Express is the easiest to use residential design program available. This program was designed specifically to introduce clients to the simple creation of floor plans, 3D models, and interior design concepts.
Envisioneer Express can also be used as a viewer to study models created in many other products on the market today including Envisioneer 3.0.
Envisioneer uses real world objects such as walls, doors, windows and stairs. These objects make creative designs fast and easy, and allow you to achieve instant 3D images with a simple point and click approach."

For direct download (without the fill-in form) try Association of Shareware Professionals: Portable Application Description (PAD). File size 38MB.