Some time ago I tested the ‘BP Groups Suggest Widget’ (http://buddydev.com/plugins/bp-group-suggest/) from Brajesh Singh, which gave me the idea to extend it, since I needed the groups suggestion to also take into account more user data.
So the result, was BP Groups Suggestions plugin.
The plugin adds “Suggested groups” functionality into Buddypress groups.
By default, it uses the user’s friends’s groups in order to suggest groups of the login user, but this can be extended throught available filters.
It adds a “Suggested group” tab into the Groups Directory page, and also a widget “Suggested groups” is available.
The login user can hide groups from suggestion list, by pressing the “Remove group”, either through the widget, the “Suggested groups” tab or by the group’s homepage. Also the login user can reset the hidden suggestion list. The plugin uses various ‘filters’ so a developer can extend it, for example to include admins specified groups as suggested, or to exclude groups from suggestion list.
You can download the plugin from http://wordpress.org/plugins/bp-groups-suggestions/