Some of the sites you have to create an account on, while this is time consuming it's for the better. Creating profiles allows me to build my brand and reputation as I can explain my profession and promote my services. I can also drop a link back to my site other other Social Content to get more followers and ultimately more targeted traffic.
This list is interesting and can have huge potential to increase visitors and followers because they all have huge followings and receive massive amounts of traffic to their respective sites. All you have to do is find a correlating topic and your in business!
Haydn says he will continue to update the list, so keep an eye on that article as new marketing opportunities will become available.