Facebook is the most popular with 200 million users. You can join any number of networks organized by city, workplace, school, and region. On your profile page, you can upload photos and albums and there's a Wall where your friends can post messages to you. You can add friends, send them messages, and update your profile to tell your friends what's new. Which leads us to Twitter, a micro-blogging site where you can push out messages or follow the 140-character or less "tweets" of your favorite people (celebrities or journalists or friends). This is so messages can be written and sent over SMS on mobile phones. You can share links that point to in-depth articles behind abbreviated URLs.
Examples of sites offering this service are tinyURL.com, dwarfURL.com and ReadThisUrl.com.
In addition to social networking and link sharing, Twitter has added a search box for a real-time view into conversations on any topic. LinkedIn is a business networking site used by professionals who stay in contact to further their career objectives. Members can exchange job leads and business opportunities and find expert advice from people in their industry.
Social media sites are also online communities where you can find and share news stories, links, Websites and post comments. In the case of Digg,
stories are submitted, commented and voted upon to establish democratically their promotion rank; only the most "Dugg" stories make it to the homepage. Stumble Upon is a Website sharing service. Featured on your profile page is your photo and "fave" sites you've tagged from among dozens of categories. Del.icio.us allows you to bookmark and organize Websites in one place, so you can get to them from any computer.