One way you could do this is by using [freestyle][1]:

<!-- 1. Enter edit mode (Tab) and -->

1. Create a transparent material and assign it to your objects:

 ![enter image description here][2]

2. Enable freestyle in *Render settings*:

 ![enter image description here][3]

3. In *Render layers*, set the line visibility to QI range and set the end to 1:

 ![enter image description here][4]

 Think of the QI range like a sort of depth index; faces directly visible to the camera are 0, faces behind those faces are 1, faces behind those faces are 2, etc.

 By only rendering lines on faces between 0 and 1 (inclusive), you can get a result like in your example image.

----

Or you could use wireframe materials:

![enter image description here][5]

See [this question][6] for details.


  [1]: http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Freestyle
  [2]: https://i.sstatic.net/mNjzV.png
  [3]: https://i.sstatic.net/s0rPP.png
  [4]: https://i.sstatic.net/buFCZ.png
  [5]: https://i.sstatic.net/mo2ZF.png
  [6]: http://blender.stackexchange.com/a/2785/599