1. Facebook 

Facebook is a social utility that connects people with friends and others who work, study and live around them.

Alexa Rank - 2 
Estimated Monthly Visitors - 900,000,000

2. Twitter

Twitter is an online social networking service that enables users to send and read short 140-character messages called "tweets". Registered users can read and post tweets, but unregistered users can only read them.

Alexa Rank - 8 
Estimated Monthly Visitors - 310,000,000 

3. LinkedIn 

LinkedIn is a business-oriented social networking service. Founded in December 2002 and launched on May 5th, 2003, it is mainly used for professional networking.

Alexa Rank - 9 
Estimated Monthly Visitors - 255,000,000 

4. Pinterest

Pinterest is a web and mobile application company that offers a visual discovery, collection, sharing, and storage tool. Users create and share the collections of visual bookmarks (boards).

Alexa Rank - 26 
Estimated Monthly Visitors - 250,000,000 

5. GooglePlus 

Google+ (pronounced and sometimes written as Google Plus) is a social networking and identity service that is owned and operated by Google Inc. Google has described Google+ as a "social layer" that enhances many of its online properties, and that it is not simply a social networking website, but also an authorship tool that associates web-content directly with its owner/author.

Alexa Rank - 1 
Estimated Monthly Visitors - 120,000,000 

6. Tumblr 

Tumblr is a microblogging platform and social networking website founded by David Karp and owned by Yahoo! Inc. The service allows users to post multimedia and other content to a short-form blog.

Alexa Rank - 34 
Estimated Monthly Visitors - 110,000,000 

7. Instagram 

Instagram is an online mobile photo-sharing, video-sharing and social networking service that enables its users to take pictures and videos, and share them on a variety of social networking platforms, such as Facebook, Twitter, Tumblr and Flickr. 

Alexa Rank - 36
Estimated Monthly Visitors - 100,000,000 

8. VK 

VK is the largest Russian social networking service in Europe. It is available in several languages, but particularly popular among Russian-speaking users around the world, especially in Russia, Belarus, Kazakhstan, Uzbekistan and Ukraine.

Alexa Rank - 21
Estimated Monthly Visitors - 80,000,000 

9. Flickr 

Flickr (pronounced "flicker") is an image hosting and video hosting website, and web services suite that was created by Ludicorp in 2004 and acquired by Yahoo in 2005. In addition to being a popular website for users to share and embed personal photographs, and effectively an online community, the service is widely used by photo researchers and by bloggers to host images that they embed in blogs and social media.

Alexa Rank - 91 
Estimated Monthly Visitors - 65,000,000 

10. Vine

Vine is a short-form video sharing service. Founded in June 2012, it was acquired by microblogging website Twitter in October 2012, just prior to its official launch. The service allows users to record and edit six-second long looping video clips, and revine. Revine is where users can share other peoples posts with followers. Some Vines are revined automatically based on what is popular.

Alexa Rank - 1,172
Estimated Monthly Visitors - 42,000,000
Article published on Official Blog Of SIMUS