I love the way these ones use the wall space to create a house shape, and have such clean modern lines.
This is a very simple one, nicely decorated with some Orla Kiely prints and little wooden dolls.
You can read how this dolls house was created here.
And finally, the size of the photo below probably doesn't do this example justice. Using Ikea Expedit shelves, each room has its own little occupant and distinctive style. Check our the shoe room !! (Via weheartit.com)