The potential offered by the development of quantum technologies has been exploited in supporting the already disruptive power of machine learning in many real-world scenarios and applications. This work reviews the application areas of the novel field of quantum machine learning and the conjunction of machine learning techniques in a quantum framework. The analysis and categorization of the reviewed literature are supported by the clustering of the labels assigned to each analyzed article so as to find connections among them. The main results of the analysis presented include the identification of the algorithms used to tackle commonly useful tasks and the domains in which these techniques are applied.