Software to do Duplo train track layout? Anyone know a way to create with a software DUPLO train track layout?  

The only thing I found is:
http://www.anyrail.com/index_en.html

It's a bit overkill for what I need and it's $US60, although the limited version can be used free.

LEGO has a track planner for non DUPLO track.
http://www.lego.com/en-us/city/trains/track-planner

If I can't find something, I'll probably try to do it myself (I have a background of tools programmer in video game industry)
I would recommend BlueBrick, which is a versatile LEGO layout editor by Alban Nanty.

Apperently it has Duplo parts too, so I believe it should meet your needs. It can actually do much more for your layout planning needs (including modular tables if your club has some, for example), so maybe you'll consider it overkill as well, but since it's specifically made for LEGO layout I think you should be hapy with it.

Disclaimer: I have never used it for Duplo myself - if you do, feel free to share your experience with us in a comment.