Ontologies are used to represent a variety of domain knowledge and data collections, scopes, viewpoints and linked heterogeneous information sources. They range from simple topologies to highly structured knowledge bases with complex relations. When mapping or aligning two or more ontologies an efficient user support is needed so that the users can understand the prerequisites and the consequences of the alignments. Information Visualization techniques can help to facilitate user understanding of the ontology alignment results. In general, a lot of work in visualization of ontologies exist. We found an enormous number of ontology visualization tools by a literature study. Many of them apply graph visualization but there are other approaches as well. We have identified interesting solutions for dealing with the complexity of large ontologies. Ontology engineering, ontology mapping and alignment can benefit from Information Visualization. Our collection is a starting point to demonstrate the usefulness of Information Visualization techniques, however, a detailed evaluation would be the next step to consolidate this research area and help to boost the adoption of ontologies in common Web applications.