Breakdown is a nuke panel plugin with which you can create breakdowns of your nuke scripts in just a few seconds. Install it and go to pane->breakdown to pt it inside your layout. Just add the nodes, that you like to appear as breakdown steps to your breakdown list and click on 'make break down'. Then all breakdown steps are generated automatically and displayed in a LayerContactSheet. If you decided so, an individual write-node is added to each breakdown step with already set up render path.

How to install breakdown

Download breakdown and copy it into your nuke home directory.
In your init.py add these line:
nuke.pluginAddPath('breakdown')

A video about how breakdown works, further information and how to instal it can be found here:

http://www.leafpictures.de/breakdown

Update:

breakdown v1.1: fixed a little bug concerning displaying the breakdown image (now relative path)