Google Sketch Up

Sketch up by Google is A Great Software. I discovered few time ago. I thing is very practical in order to make project because we can create and modify as we want, It's very easy very quick and FREE. The only problem is you can't export in 3D file like Autocad or 3D studio but try to use it here
If you have Google Earth you will be able to see your project in ground like this house I made in Portsmouth, uk.

Conceptual shelter