SketchUp, free 3D modeling

Free 3D modeling software , formerly a Google product, it can design anything as simple as a cup to more elaborate, like an entire city.
It was previously abole to interface to Earth with Building Maker to include modeling of actual buildings and enrich the map of the World. But this software was dropped by Google on June 2013.

SketchUp was sold by Google to Trimble, but support should remain available on http://sketchup.google.com.

The paid version includes a tool to make arrangement for 2D drawings and interactive presentations. It allows you to exchange models with other CAD (computer aided design) products. And it also includes Style Builder to generate a plan modeled from a sketch made by hand.

Features of SketchUp:

A model is made from lines and faces. A face is composed from lines and it becomes an object used in a plan that you can move, resize, combine with other objects.

To switch from 2D to 3D, we have an extrusion tool unique to Sketchup, named Push/Pull.
A rectangle becomes a box by simply moving the mouse with this tool.

We go further by making an extrusion along a path which allows for specific forms, thanks to the Follow Me tool

Another tool lets you paint or apply a texture on a surface.

The objects are then combined to produce more complex objects such as the houses on the image above. For that, two tools are available. Groups to build composite objects and Components that allows you to make relational copies : when a copy is modified, the others are too.

Advantages of Sketchup:

Its drawbacks:

Tutorials and extension:

More 3D tools: