BuddyPress Auto Friendship Pro download gpl allows you to add users as friends to the newly registered member. It allows site admin to create multiple users list which can be automatically added as friends to new members.
The plugin can be used to create global list(The users from this list will be always added as friend to the new user) as well as conditional lists. You can specify one or more conditions for matching list to new user(based on xpeofile field data or member type or role). Users from all the matching list will be added as friend to the new user.