  The emergence and popularization of online social networks suddenly made
available a large amount of data from social organization, interaction and
human behavior. All this information opens new perspectives and challenges to
the study of social systems, being of interest to many fields. Although most
online social networks are recent (less than fifteen years old), a vast amount
of scientific papers was already published on this topic, dealing with a broad
range of analytical methods and applications. This work describes how
computational researches have approached this subject and the methods used to
analyze such systems. Founded on a wide though non-exaustive review of the
literature, a taxonomy is proposed to classify and describe different
categories of research. Each research category is described and the main works,
discoveries and perspectives are highlighted.
