Hiranthi

Remove links for parent-items, add a is-parent class and/or add the parent-item to the submenu.

wp_list_pages tweaks

Remove links for parent-items, add a is-parent class and/or add the parent-item to the submenu.

Didier Sampaolo

This WordPress plugin is oly one function. It takes exactly the same parameters as wp_list_pages, except for child_of, which is used internally. 
When called on in template file, it will list : 
* on the homepage of the blog, every page and subpage (default, this can be overriden by parameters) 
* on every other page, only the pages with the same top-parent (parent of level 1)

wp_list_sub_pages

wp_list_sub_pages will list only pages within the same category (top-level parent) as the current page.

wp_list_pages tweaks vs wp_list_sub_pages