Liferay 6 offers feature of Site Templates , where in you can design a site template . Using the newly designed template you can create multiple communities and organization on the fly. Just apply the template while creating those communities .
Site templates is nothing but a community which will act as a template for new communities. It will have Pages , Portlets , Content just as a regular community can.
Here are the steps to create a site template and create a community using the newly created site template.