An ever increasing number of Web sites that allow users to easily collaborate, produce, and share content and interact have turned the Web into a more dynamic social place often referred to as Social Web. One form of Social Web sites is collaborative tagging systems that allow their users to annotate Web resources using tags, thus intuitively organizing them and making them easily findable. Tags would have been much more useful if collaborative tagging systems had been collaborating and allowing for integration of their tagging metadata. In this paper we address this issue of lack of collaboration by suggesting an approach for achieving that collaboration. We also present a concrete system called TagFusion that we developed to test the feasibility of the suggested approach. Special attention has been given to the strategies for attracting collaborative tagging systems to integrate using TagFusion, as well as to the possibility of involving artificial entities in the annotation process in accordance with the Semantic Web vision.