I think this is what you're looking for.  (Make sure you read through it all)

Hello,
I'm in the process of setting up a blog, it may be my first attempt at movabletype but I'm a programmer for a living so I'm not completely fresh.
My inquiry is how I should handle my need for subcategories. I'm setting up my site to have three different blogs, or categories, if you like. Each of these separate blogs/categories are to have different categories within them.
Now, my way of solving this is to set up three different blogs to represent the three blogs/sections and within these keep different categories. Fine. Except on the entry page of either of these three blogs I want to list the five most recent entries in all three blogs by headline.

The question would be how to list the recent entries of an arbitrary blog which you know where the xml-feed is. I guess, unless an even more smooth solution exists.

Thanks a bunch in advance to any and all answers.
/Tomas Jogin, Sweden. (t_jogin(at)hotmail.com)