Reverse sync CiviCRM groups to Drupal organic groups
We use civicrm_entity module + rules to do things like that. This blog gives a recipe for relationship to OG. 

There are a couple of general civicrm+rule blogs

http://www.jackrabbithanna.com/articles/simple-rule-example-using-civicrm-entity

http://www.fuzion.co.nz/blogs/complex-civicrm-relationship-role-synchronisation-recipe

But neither are specifically to OG - I think there is one somewhere though - or else maybe an og rules feature - if I find it I'll paste it in