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Being online is all about staying in touch, and Ubuntu is no slouch in this regard. Ubuntu offers a wide range of applications, including a full-featured e-mail program, called Evolution, as well as an instant messaging client called Empathy, which allows you to connect to the most popular instant messaging sites, such as GTalk and MSN.
You can install a Skype client that allows you to connect to the popular service to make voice and video calls to other Skype users or to telephones; and you can install an open source alternative to Skype called Ekiga.