Hey Patrick,
Not sure exactly what you mean, but I think you want to organize groups into categories? You could try this: http://wordpress.org/plugins/bp-group-hierarchy/
It’s not perfect, but it may work for what you’re trying to do. You could put groups in hierarchies so you could have a top level Football group, and then groups within that hierarchy (child groups) that are all related to Football. Then you could find the link for that hierarchy and place it in the nav menu. Something like that 🙂