SketchUp

SketchUp is a 3D modeling program optimized for a broad range of applications such as architectural, civil, mechanical, film as well asvideo game design and available in free as well as 'professional' versions. 

The program highlights its ease of use, and an online repository of model assemblies (windows, doors, automobiles, entourage, etc.) known as 3D Warehouse enables designers to locate, download, use and contribute free models. The program includes a drawing layout functionality, allows surface rendering in variable "styles," accommodates third-party "plug-in" programs enabling other capabilities (near photo realistic rendering) and enables placement of its models within Google Earth. 

I think SketchUp is a really good program, you can do a lot of things and it’s not so difficult to use it but you have to see some videos tu understand a little bit how it works.