This is going to be (if not already is) the most comprehensive list of social networking sites that you will find on the web together with information about how to join, and what you can get out of social networking at both business and personal levels.
Many people use social networking websites simply to keep in touch with friends and family, by posting regular updates contacts can keep in touch with what you are doing at any time wherever you are on the globe.
From a business perspective, more widely known as
social media marketing
however this concept is not widely understood. If you would like to know more about it then take a look at my section dedicated to social media marketing.
Having made that quick distinction between business and pleasure is fair to say that many social networking websites cover both so I'll try to segregate the links below but inevitably there will be some sort of crossover. As always, please remember that just because this list of links it on my site it doesn't constitute a recommendation from me.