wow, really had to rework the main page to get the categories part to work the way I wanted, including implementing a template filter.  I haven't implemented anything about the subcategories yet, as I'm not sure how I want to handle that.
I got the subcategories working nicely now, the django regroup function is really nice.  However, I sort of messed up the trader/posts page in doing so, really I just need to give it its own template instead of recycling.  There are a lot of little breadcrumb type things I could implement, but I'm going to leave it for now.
fixed the trader/posts issue, and fixed the pagination in the categories pages which were a bit wonky before.