Since their emergence around 2005, social networking sites have been growing, potentially transforming our daily lives and even the area of mainstream education. Despite such tremendous influence the SNS services have on our society and education in general, little research has been conducted concerning the application of social networking sites for foreign language learning and teaching purposes. The aim of this study, therefore, is threefold: 1) to provide the introduction of social networking sites and to examine how they have been used for general education; 2) to examine theoretical bases upon which the incorporation of social networking sites into foreign language learning and teaching is based with special reference to the Noticing Hypothesis and the Output Hypothesis; 3) to review some examples of using existing social networking sites for foreign language learning programs. Cases from Facebook, Orkut, Twitter, and Livemocha will be discussed in terms of course design, the nature of tasks employed, and outcomes. Implications from the case reviews will be followed to help teachers integrate some of the features of SNS-based language learning and teaching into their curriculum. Finally, benefits, challenges, and future outlook of this newly-rising area will be discussed.