This chapter has demonstrated an elegant way to visually represent ontological data. We have described how the Cluster Map visualization can use ontologies to create expressive information visualizations, with the attractive property that classes and objects that are semantically related are also spatially close in the visualization. Another key aspect of the visualization is that it focuses on visualizing instances rather than ontological models, thereby making it very useful for information retrieval purposes. A number of applications developed in the past few years have been described that prominently incorporate the Cluster Map visualization. Based on these descriptions, we could distinguish a number of generic information retrieval tasks that are well supported by the visualization. These applications prove the usability and usefulness of the Cluster Map in real-life scenarios. Furthermore, these applications show the applicability of the visualization in Semantic Web-based environments, where lightweight ontologies are playing a crucial role in organizing and accessing heterogeneous and decentralized information sources.