The rise of Web 2.0 tools has led to the rapid development of a number of applications that enhance collaborative work. These include social bookmarking systems (SBS) that provide users with the reference (marked), description, classification and the possibility to share resources with other users. In this paper, all the applications of SBS are addressed: functional features, nature, and restrictions. Next, one of these tools, Diigo, is analyzed, taking into account its possible uses and benefits for researching and education. In the fourth section, a comparison between different methods of storing bookmarks is carried out in order to highlight the advantages of Diigo and its differentiating features. This comparison is completed through a SWOT analysis of the kind of tools used in a 30-user community. To close, some conclusions and possible future directions of investigation are outlined. Web 2.0 has created new applications with remarkable socializing nuance, such as the SBS (Social Bookmarking Systems). Rather than focusing on the relationship between users, the SBS provide users with the necessary tools to manage and use information that can later be shared. This article presents a description, analysis, and comparison of different SBS, which are categorized as web applications that help to store, classify, organize, describe, and share multi-format information through links to interesting web sites, blogs, pictures, wikis, videos and podcasts. Also emphasized are the advantages for learning and collaborative research that SBS produce. In this paper, Diigo will be specifically studied for its contribution as a metacognitive tool. Diigo shows the way each user learns, thinks, and develops the knowledge that was obtained from the information previously selected, organized, and categorized. Thus, the information becomes highly valuable, and knowledge is cooperatively built. This knowledge induces collaborative learning and research, since the tags that describe marked resources are shared between users. Consequently, they become meaningful learning resources that provide a social dimension to both learning and online research processes.