1) This extension contains all categories display as combo
2) If selected category has subcategory then new ajax based combo will added
3) Second step will be repeat until subcategories found
4) If selected category/subcategory don't have subcategory it will redirected to the product listing page
5) Extension is working for root category as well as for subcategory page
6) Block can be added for static content page as:
{{block type="ajaxcategories/list" name="ajax_categories" template="ajaxcategories/list.phtml" }}