Display subcategories in custom menu automatically

Dear users of www.ads-software.com,

I’m currently building a news site where we sort all posts by location using categories. This means we have lots of hierarchical categories. I wish to enable visitors to click a menu button for the category they want to view. Adding categories to the menu isn’t difficult, but since I have quite a lot of them, I would like to automate that process.

I would like to show all child categories in the menu, without having to add them manually. I’ve tried to find other people with the same problem and maybe even a solution both here and on other fora, but I can’t find any. Can you help me?

Jeroen