Interesting article about two free plugins you can download for free. For the whole article, click here.
Also check the comments below.
Sketchup is, by far, the easiest tool for modeling. Google acquired this software in order to crowd-source the 3D modeling of the earth, since anyone can use it to model their house, school or favourite building. But being simple and fast doesn’t mean it lacks on features.
You can enable several options available on the free standard version, or go pro for more. Also, you can extend it via plugins. Below, two plugins I have found very useful, and also available for free.