LinkedIn, Facebook, Twitter, YouTube or Friendfeed (Friendfeed is essentially a social aggregator but no less than social networking sites in effectiveness) are certainly some excellent Social Networking sites for self- promotion activities. MySpace, it needs to be mentioned, has over 185 million users, split evenly between men and women and of various age groups.
FaceBook has over 110 million readers, predominantly women and most of these users are under 30 years old and nearly 50% of all FaceBook users are located in the U.S., Great Britain and Canada. LinkedIn has over 26 million readers, and it is said that the average age of readers is 41 predominantly constituting of men..Twitter has a relatively small base with 3 million readers, two-thirds of whom are men between 18 to 34 years old. (Source: SocialNetworkingWatch)
Apart from general networking sites like MySpace and Facebook, there are many smaller networks that focus on professionals and ideally suited for budding entrepreneurs and to name few - Entrepreneur Connect, PertnerUp, Konnects, Ryze, Biznik, Cofoundr, StartupNation, Upspring, Fastpitch and Xing.
Image Credit: Wikimedia Commons.