LinkedIn is a powerful, professional social networking site. In my opinion, it’s better than other similar sites - the interface is cleaner and the free service has much more to offer than its competitors. Earlier, it seemed to be tech and business focused. However, the numbers of public health professionals utilizing the site appears to be increasing.
I’ve started a group there for Global Public Health. Joining allows you to view the profiles and connections of all other members, and vice versa. Feel free to join and connect to others working in the field. I need to approve each person individually, so it might take a day or two to be added, depending upon my time.