http://groups.yahoo.com/group/PCGenListFileHelp/
http://groups.yahoo.com/group/pcgen/
Try the ListFileHelp group first.
Two other suggestions:
-If you downloaded the FULL version of PCGEN, under the program directory, you will find a \docs directory. Inside it, starting with index.html, is a rather extensive HTML documentation of all of PCGEN's tags in their .LST files.
-Furthermore, There are custom content creators in the program, under the Tools --> List Editors menu. It allows you to create custom classes, deities, domains, feats, languages, races,skills, spells, etc. and the item editor in the program allows you to create custom items, as well. THe simplest way is to copy an existing concept (feat, class, etc.) that does close to what you want, and modify it.
If you want to create your own dataset from whole cloth, it's best to dive wholly into that documentation I mentioned first, and then start working, and ask for assistance when you come to something you don't understand. Although the PCGEN community is very helpful and polite, it's a common point of courtesy to get the gist of how LST files are created first by attempting it yourself. They get a lot of requests to "make this for me", and I can imagine it would get tiresome if one heard requests like that all the time. Not saying you would, of course, but I just wanted to arm you with all the info you will need to dive in.
Good luck!
Henry