Carnegie was the originator of the "How to win friends.." stuff. His influence can be seen in many more recent techniques, including EST, and its offspring "The Forum". The bulk of it is hooey, but it is very well pacakged hooey, and it gets its own share of rabid followers.
What is very interesting about the Carnegie seminars is that many of the very same techniques were repackaged and presented as part of the Service Meetings.