You’ve undoubtedly heard the names Facebook, MySpace, and Friendster thrown around in recent years. These sites are examples of online social networks, and are a tiny fraction of the number of similar sites taking root on the Web. We're all familiar with social networks offline; they could be one’s professional contacts, college friends, or family members. Online social networks take this idea of connecting with others and make it digital. Whether it’s for fun, business, romance, or any other reason, more and more people are interacting over the Net. To learn more about this phenomenon, and to do some networking of your own, use the resources provided in this guide. For a Spanish-language version of the Guide, click here.