The Foundation established two other kinds of affiliate groups: thematic organizations and user groups as alternatives to chapters. The first is related to a specific activity or "topic" with the two groups I know of being the spinning off of the US Ed program into this category and one group related to medicine.  User groups are more informal and dont require as many hoops to have some kind of official status. we´re working on creating one of these right now for students at my university (there are student groups supposedly, but they dont have the kind of recognition that these organizations do).

The page on thematic organizations is at https://meta.wikimedia.org/wiki/Wikimedia_Thematic_Organizations
and the one on user groups is at https://meta.wikimedia.org/wiki/Wikimedia_user_groups