Using a combination of Ultimenu (http://drupal.org/project/ultimenu) and Menu block (http://drupal.org/project/menu_block)

Ultimenu allows you to create a new menu block based on a current menu. From that each menu item you select adds a new region to the theme in to which you can place blocks.

Then using Menu Block you can create the different sub-menus for the main child terms. It is a fair amount of work to set up but once set up is far better than Superfish in my opinion. If you are a coder you can automate most of it thanks to Menu Block providing an API to generate blocks programmatically.

Then you just add the menu blocks in to the necessary regions and it's not just limited to menu blocks, you can put any blocks in there including Views.