This BuddyPress (version 1.8+) plugin allows you to stick groups on top of the groups directory front page. Administrators can set a group as sticky from the WordPress backend group Admin UI.
NB : version 1.0.3 of this plugin requires at least BuddyPress 1.9
The sticky groups will appear whatever the sort order of the groups loop is. As soon as a search query is performed, the sticky feature won't be applied so that the result of the search remains consistent.
http://vimeo.com/74177071
This plugin is available in french and english.
You can download and install BP Sticky Groups using the built in WordPress plugin installer. If you download BP Sticky Groups manually, make sure it is uploaded to "/wp-content/plugins/bp-sticky-groups/".
Activate BP Sticky Groups in the "Plugins" admin panel using the "Network Activate" (or "Activate" if you are not running a network) link.