There are a variety of use cases for Graph Portal. Here is a list of some of them. The potential uses are far beyond the limited list shown here.
Web Portal: Portal for various types of content
Content Management: Organize web content, links, web page fragments etc.
Wiki: Organize your knowledge in easily retrievable form.
Mind Map: Organize your thoughts.
Academic: For modeling graph and testing graph theory.
Family Tree: Or any similar hierarchical data like friends, people you meet etc
Code Snippets Organize snippets of code for various technologies
Project Organizer Organize dependencies of tasks