Call only one category and show childs

I have a lot of categories in my WP installation (nearly 60), because I?′m going to use my site not only for bloggin, but for photo gallery (I found an interesting method), downloads, and more things. My question if there is a method to call only one category and show his childs, instead of put all the ID of the exludes categories on the <?php list_cats(); ?>. I don?′t know if I?′m going to create new categoriess or sub-categories on the future, and I don?′t want to go modifying each <?php list_cats(); ?> to exclude new categories (actually, there are 7 diferents sidebars in my theme, with a <?php list_cats(); ?> on each)