What are examples of social media sites?

There are lots of social media sites across the world wide web today and this includes the following sites with their recent statistics according to Wikipedia:

1. Facebook - As of July 2011, Facebook has more than 750 million active users.

2. Twitter- with 200 million users as of 2011.

3. Google+ (Google Plus)- On July 14, 2011, Google announced that Google+ had reached 10 million users just two weeks after it was launched in a "limited" trial phase. After 4 weeks in operation, it had reached 25 million unique visitors.

Attached on related links is the list of Social Networking sites.