I found an interesting plugin which lets you assign categories their own, different themes. I tested it on one site so far: http://aghca.org. I'm using Atahualpa as my main theme. Click on Current Activities in the Page menu to see that category with a different theme, one I made in Artisteer.
Perhaps Flynn has already put this functionality into Themeframe, but I'm thinking it would be great if we could have various versions of Atahualpa, with different options in place, for different parts of the site. In effect it would be like using the plugin, but we'd have the basic look and feel of Atahualpa throughout the site, with any customizations we need per category.
The plugin is here: http://get-your-stuff.com/