1. Facebook

facebook.com
An online social networking site that connects people worldwide, to register and create an account to use to keep up with family, friends and colleagues. Share status, upload photos, share links and videos.
1,100,000,000 – Estimated Unique Monthly Visitors

2. Twitter

twitter.com
Social networking and microblogging web interface. It enables registered users to send and read short ( 140-character) messages called “tweets”.
310,000,000 – Estimated Unique Monthly Visitors

3. LinkedIn

linkedin.com
A business oriented networking tool to find connections, job candidates, industry experts and business partners. LinkedIn is really a huge database of professionals. It allows registered users to maintain a list of contact of people they know and trust in their area of interest.
255,000,000 – Estimated Unique Monthly Visitors

4. Pinterest

pinterest.com
Pinterest is a visual online pinboard where users you can post collections of interest or things they love. Posting is known as pinning. Users can browse, repin and follow collections created by other users.
250,000,000 – Estimated Unique Monthly Visitors

5. Google +

plus.google.com
Social network and microblogging site from search engine giant, Google. It integrates other Google services with an aim to make sharing on the web easy, fun and informative. It is a place to connect with like-minded people in groups called community. Create your own community, share images, videos, links and texts with the world.
120,000,000 – Estimated Unique Monthly Visitors

6. Tumblr

tumblr.com
A microblogging platform and social networking website. It is a cross between a social networking site and a blog. It allows registered users to post text, images, videos, links, media to their own customisable blogs.
110,000,000 – Estimated Unique Monthly Visitors

7. Instagram

instagram.com
Instagram is an online mobile photo-sharing, video-sharing, and social networking service. Snap and upload pictures to share with other users and also other networks such as Facebook, twitter and Google +.
100,000,000 – Estimated Unique Monthly Visitors

8. VK (originally VKontakte)

vk.com
VK is not only the largest Russian social network, it also the largest social network in Europe. It is available in several languages, but is especially popular among Russian-speaking users. It is considered the Russian equivalent of Facebook. Registered users can have profiles and pages, much like Facebook – update status, post images, videos, text. Join groups of your interest and connect with others.
80,000,000 – Estimated Unique Monthly Visitors

9. Flickr

flickr.com
Photo management – hosting and sharing service. Host and share hundreds of your own pictures on Flickr for free. Join groups of interest and connect with others.
65,000,000 – Estimated Unique Monthly Visitors

10. Vine 10

vine.com
Vine is a Twitter owned short-form video sharing service where users can share six-second-long looping video clips. The idea is to create quick, easy and interesting short films to share with your friends on Facebook, Twitter and the world at large.
42,000,000 – Estimated Unique Monthly Visitors

Visitor number source ebizmba.com