In this paper we present a review of systems that follow the novel paradigm of Social Semantic Bookmarking. Social semantic bookmarking allows for the annotation of resources with tags extended by semantic definitions and descriptions that also evolve collaboratively within the same system. We analyzed nine different systems that extend social bookmarking in the direction of more semantics; i.e. that enable their users to add semantics to the folksonomy. We studied the systems regarding the realization of the social semantic bookmarking paradigm, the features offered to the users to add semantics, what kind of semantics can be added, and how the system makes use of the semantics. We will present commonalities, main differences and distinctive features, and future trends.