I've been looking around lately for some home design ideas and came across this torrent below. It should be all you need if you are looking to design your own house or at least get some design ideas from.

There are 2,740 \".DWG\" files in 1.54GB once extracted.
Be sure you have AutoCAD or a DWG viewer to use these.

Here is the torrent for home designs and floor plans:

Hundreds of house floor plans for autoCAD .dwg (download torrent) - TPB

You will need to download a program to view these files as they are in .DWG format.
Here is a link for the viewer:

Autodesk - DWG TrueView - DWG TrueView Download

You may also need the .NET framework 3.5 from Microsoft; if you haven't got it installed already here is a link for that:

Download details: .NET Framework 3.5

That should be all you need. There are lots of good designs to choose from or take bits and pieces and use for your own floor plan.