Peter Westwood

This plugin allows you to run loops within your WordPress templates where you query for children of the current page.
The plugin extra arguments to the list of arguments supported by query_posts().
The query argument <code>child_of</code> is used to add a WHERE to the database query to limit the pages returned to those with a post_page equal to the argument provided.
The query argument <code>child_limit</code> is used to limit the number of pages returned.
The query argument <code>child_offset</code> is used to offset the limiting to allow for pagination if required.

PJW Query Child Of

This plugin allows you to run loops within your WordPress templates where you query for children of the current page.

alekc

Sometimes you don’t want to show parent directories in permalink because they are not really necessary or because you know that in the future your child directory will change it’s parent.
For example: 
+Work in progress 
–Site 1 
–Site 2 
+Work Finished 
–Site 3
In this case Site 3 originally have been part of “Work in progress”, and on job done it has been moved under “Work Finished”.
So if you install this plugin your link will be transformed in this way:
domain.com/parent_category/child_directory/post_name => domain.com/child_directory/post_name 
domain.com/category/parent_category => domain.com/parent_category 
domain.com/category/parent_category/child_directory => domain.com/parent_category/child_directory

Remove Parents

Remove Parents is a tiny plugin which remove "category" and parent categories from permalink.

PJW Query Child Of vs Remove Parents