[CupOfJava]

I want to model my home in 3D, with measurements. What's a good free alternative to autocad for that?

[Sileni]

Doesn't have all the functionality that AutoCAD does, and there are some usability issues if you're really comfortable in AutoCAD already, but I imagine FreeCAD [0] would work well for your use case.

[0]: https://www.freecadweb.org/

[acidburnNSA]

I'm particular the BIM workbench is looking pretty slick these days [1]

[1] https://www.freecadweb.org/wiki/BIM_Workbench

[trentlott]

Blender allows for the use of human units. It also contains engines for physics and lots of videos explaining how to do interesting things, including allowing for Python scripting

Choosing a very popular free platform has benefits (blender.org)

[sanbor]

SweetHome3d is what you're looking for: http://www.sweethome3d.com/

[LeonM]

Sketchup [0] has a free version for personal use

[0] https://www.sketchup.com/