Quote from their web site:

Treebolic is a Java component (widget) whose purpose is to provide a hyperbolic rendering of hierarchical data.
A tree is rendered with nodes and edges but display space is subject to a particular curvature (hence the name) : more space is allocated to the focus node while the parent and children, still in the immediate visual context, appear slightly smaller. The grandparents and grandchildren are still visible but come out even smaller. As we move away from the focus node, less display space is allotted to the nodes, which gradually disappear towards the disk’s border, as though the whole hierarchy were seen through a fisheye lens.
Wrapped as a Java applet, the Treebolic widget can be embedded in a web page. Nodes may then contain hypertext links and the browser to other web pages.
The tree is dynamic (animation brings the focus node to the center) and responds to user interaction.

http://www.franz.com/agraph/gruff

Use Gruff to display visual graphs of subsets of a store’s resources and their links. By selecting particular resources and predicates, you can build a visual graph that displays a variety of the relationships in a triple-store. Gruff can also display tables of all properties of selected resources or generate tables with SPARQL queries, and resources in the tables can be added to the visual graph