Is there a free service that allows its users to create a group with subgroups?

[Anthony]

Would prefer something available through an established social media site, but I don't think Facebook or Google + has this ability. It doesn't need to be a literal folder/subfolder hierarchy, just appear that way on the national view. A page for the central organization with links on it to the sub organizations or franchises attached to it. This is currently a non-profit, so trying to keep the cost as low as possible. I know a web page could be created, but need something as easy and connected as FB/Google +.

[fatBig608]

Perhaps you could join Dreamwidth and create a community on there.

[Conzortia]

LinkedIn permits this, as well. You can create a group for free & sub-groups can be added.