Cakephp-navigation is a project mainly written in PHP, it's free.
Blended support for navigation in various forms for cakephp apps (not yet fully functional) -- the helper is ok, its a start
git submodule add git://github.com/sams/navigation.git plugins/navigation
add Navigation.Navigation to helpers and Navigation.Menus to comps
copy plugins/navigation/config/config.ini to app/config/navigation.ini and customise
epxand, tidy and implement the component menus, tweak the helper use Set class and other aspects of cake to enable menu items to be combined and sorted so that menu items can be added to a menu in specific position