Ashampoo 3D CAD Architecture is a very complete design tool which can help you plan and visualise anything from a single room to an entire building, and its surrounding grounds (carport, conservatories, garage and gardens, it's all here).
The program's Building Wizard - greatly extended in this version - gets you off to a speedy start. In just a moment you can choose the basic shape of your building floor, for instance (rectangle, L-shaped, U-shaped and so on). Enter the precise dimensions, add as many floors as you need, top off with the correct roof style from the 8 options on offer, and that's it: you can have the initial building shell displayed in just a few minutes.
But then, of course, the customisations begin. Outside, you might start by adding doors, windows, roof windows, maybe solar panels. Then inside you're able to set up each room with chairs, tables, shelving, lighting, cupboards, kitchen units, bathroom accessories, some electrical basics (speakers, a flatscreen TV) and the list goes on. The program doesn't have the largest object library so you're not going to be able to reproduce your living room 100% accurately, but there's enough here to be useful (and you can always import existing 3D objects in all the main formats if you need more).
If you're new to this kind of tool then you'll appreciate the sample projects included with the program. They're a little lacking in terms of interior design but there's still enough here to help you get started.
And when you've finished your project, Ashampoo 3D CAD Architecture can help you share it by exporting everything from an item list or bill of quantities to 3D models in a range of common formats (CYG, 3DS, Caligari TrueSpace, DXF, VRML, Lightwave or Wavefront objects).
But if you need still more, check out the program's big brother, Ashampoo 3D CAD Professional. It adds 2D DXF/ DWG import/ export, Maxon Cinema 4D export, a versatile Window Designer, and more roof creation and design options, amongst other options.