I don't know of any. I'm guessing most people that create themes have a solid understanding of java, .css, .html., .php, .tpl, etc., and/or know someone who can help out.

The best way to learn is to download a theme you like the base structure of and modify it to death. It will take a lot of your time but you'll end up with a satisfying theme in the end, a feeling of accomplishment and you will have learned a lot about theme structure while doing it. ***Just make sure to keep the original credits in tact*** however it is permitted to add that you modified the original theme.

If your looking to re-distribute though that's a whole other issue that can only be discussed by you and the original author.

If you're still hell bent on creating your own theme then here are a few resources to help you on your way:

http://www.karakas-online.de/EN-Book/template.html

http://www.karakas-online.de/forum/viewtopic.php?t=2645

http://www.tldp.org/HOWTO/PHP-Nuke-H...structure.html

http://www.webdesign.org/

http://www.tldp.org/HOWTO/PHP-Nuke-H...eme-rules.html