Is there a plugin to group my categories?

hi, im searching for a plugin to group all my categories into a category index page.
i have tried azindex but it is used to group all posts into a post index page.
actually i just wanted to have a category index page whereby if people click into a category only will show all the posts in it.
im currently have 5 first level categories, 10 second, 500 third, so i would like to have an index page for one of my first level category and all its child categories to be listed in a page.
anyone can help?