For lack of a better title, let me try to explain further:

I'm looking for a control that will allow me to have a library of "page elements" (such as a list of employees, or a photo gallery, or a contact form, etc) that could be dragged onto the page canvas.

The page canvas could have pre-set regions/boxes where these items could be drug into, preventing the user from screwing up the pages layout.

I'm looking for any pre-built commercial (or open-source with commercial use allowed) tools available like this.