List Private Organic Groups Publicly without giving access to the node page?
You can tell Views to ignore the access control of some of the Views. On Views 3.x, this parameter can be found under "Query Settings" / "Disable SQL rewriting", and is described as:


  Disabling SQL rewriting will disable node_access checks as well as other modules that implement hook_db_rewrite_sql().


The full nodes will stay private, so you should make sure not to link to them in the View so that your users do not land on "Access Denied" (403) pages.