ILC Folding (ilc-folding) free WordPress plugin

ILC Folding works with parent/children hierarchy of the Pages Widget. It will progressively reveal the children of each parent page. When you visit a page that has children, they will be reveal, keeping the next level children hidden.
You can see a demo at
http://www.ilovecolors.com.ar/ilctest/
Visit Page 2 to see their children. Child Page 2.1 works too.