Almost any information contained in OpenGroupware.org can be accessed using it's XML-RPC interface from almost any programming language. This opens a wide door for extending OGo with standard Linux utilities and for integration into an existing infrastructure.
Use it to dump OGo data into LDAP servers, to let OGo transfer documents into the versioned storage by email or just to import the data extracted from your old, proprietary Groupware into OGo.