Off and on for a couple of months (mostly off) I have been working on this script to model stairs in Blender. If you are interested you can download it here: www.built4living.com/stair.zip.
The zip file contains two python files (Stair_builder.py and Stair.py), two .bmps and an html help file (which can be accessed through the GUI in Blender). Stair_builder.py is the script; Stair.py is a supporting module.
Let me know if you have any questions or problems.