Facebook is a social networking website that is operated and privately owned by Facebook, Inc. Since September 2006, anyone over the age of 13 with a valid e-mail address can become a Facebook user. Users can add friends and send them messages, and update their personal profiles to notify friends about themselves. Additionally, users can join networks organized by city, workplace, and school or college. The website's name stems from the colloquial name of books given at the start of the academic year by university administrations in the US with the intention of helping students to get to know each other better.

Twitter is a free social networking and microblogging service that enables its users to send and read messages known as tweets. Tweets are text-based posts of up to 140 characters displayed on the author's profile page and delivered to the author's subscribers who are known as followers. Senders can restrict delivery to those in their circle of friends or, by default, allow open access. Since late 2009, users can follow lists of authors instead of following individual authors.

Technorati is an Internet search engine for searching blogs. By June 2008, Technorati was indexing 112.8 million blogs and over 250 million pieces of tagged social media. The name Technorati is a blend of the words technology and literati, which invokes the notion of technological intelligence or intellectualism.

Digg is a social news website made for people to discover and share content from anywhere on the Internet, by submitting links and stories, and voting and commenting on submitted links and stories. Voting stories up and down is the site's cornerstone function, respectively called digging and burying. Many stories get submitted every day, but only the most Dugg stories appear on the front page. Digg's popularity has prompted the creation of other social networking sites with story submission and voting systems.The website traffic ranked 99th by Alexa.com as of January 2010

StumbleUpon is an Internet community that allows its users to discover and rate Web pages, photos, and videos. It is a personalized recommendation engine which uses peer and social-networking principles. eb pages are presented when the user clicks the "Stumble!" button on the browser's toolbar. StumbleUpon chooses which Web page to display based on the user's ratings of previous pages, ratings by his/her friends, and by the ratings of users with similar interests. Users can rate or choose not to rate any Web page with a thumbs up or thumbs down, and clicking the Stumble button resembles "channel-surfing" the Web.

reddit is a social news website owned by Conde Nast Digital on which users can post links to content on the Internet. Other users may then vote the posted links up or down, causing them to become more or less prominent on the reddit home page. The site has discussion areas in which users may discuss the posted links and vote for or against others' comments. When there are enough votes against a given comment, it will not be displayed by default, although a reader can display it through a link or preference

Delicious is a social bookmarking service that allows users to tag, save, manage and share web pages from a centralized source. With emphasis on the power of the community, Delicious greatly improves how people discover, remember and share on the Internet.

Bebo, an acronym for "Blog early, blog often", is a social networking website, founded in January 2005. There is now tailored content targeted at UK, Ireland, Australia, NZ, US English and US Latino, Canada, France, Germany, Italy, Spain, Netherlands and India, with the site being available in English, French, German, Spanish, Italian, Dutch and Polish. Founded by husband and wife Michael and Xochi Birch, Bebo had a major relaunch in July 2005. It was bought by AOL on March 13, 2008 for $850 m (£417 m).

MySpace became the most popular social networking site in the United States in June 2006. According to comScore, MySpace was overtaken internationally by its main competitor, Facebook, in April 2008, based on monthly unique visitors. MySpace employs 1,000 employees, after laying off 30% of its workforce in June 2009. The 100 millionth account was created on August 9, 2006, in the Netherlands.

SodaHead is a dynamic discussion community where you can discover, debate and discuss issues that get you fired up. Over 1.5 million SodaHeads share their unique views on hot topics, breaking news and controversial issues and a diverse panel of staff writers provide original and exclusive content daily.