I didn't list my blog as it is still private as I am developing it.
The themes I am using are in the first post (Coraline or Twenty Ten). I am alternating back and forth between them but both basically sport the same features. Though I am leaning more toward Coraline at this moment.
Specifically posts in those two themes both have special post formatting when the post is set to an "aside" or "gallery" category.... As mentioned in the first post, I know I can easily do category filtering via PHP editing on a self-hosted blog (modifing "The Loop"), but I am specifically asking about the free wp.com blogs.
Both of these themes support custom menus (great feature) and as I mentioned, I do have a menu option already, it works fine to get me to a gallery category view when clicked, however I wanted the main index page to filter out certain post categories (specifically "Gallery" categories) as I don't want the "Gallery" category posts to show on the main blog when you first hit the site. However from further reading I found that this can't be done.
Since I don't want the user to see a mixture of gallery and regular posts on the main page, the best I can come up with is changing the first page to be static page and then have the user click a "posts" category menu item that goes to the post category archive keep the menu item I have for gallery category. Which is what I think you are suggesting (though keeping the default index view). I had already thought of that but while this will work I was kinda hoping to have the main index page show only certain categories to save the user a click to see posts when first hitting the site.
Moreover, ideally, I only want to cordon off "gallery" category posts, I want to list regular and aside posts together (the formatting of an aside is moot if its not between regular posts after all).
I think I can use set theory and create an "aside and posts" category and tag regular posts under two categories as both "posts" and "asides and posts" and asides posts as "asides" and "asides and posts" and then display the "asides and posts" category to effectively get a list of both categories and have the differentiated formatting but I haven't tried this.
I also mention the archive shortcode, only because I could create a static front page but use that shortcode on it to get a dynamic list of posts, however it doesn't support category filtering, just date filtering->though it, or another shortcode looks like my best chance to get category filtering though.