FlexViz is a graph based visualization tool written in Adobe Flex. It has support for browsing a single ontology where the concepts are represented by nodes and the relationships between concepts (e.g. "is_a", "part-of") are represented as arcs.
Here is a list of the main features:

• node and arc type filtering
• searching
• many different graph layouts
• customizable node and arc labels
• customizable node and arc tooltips
• zooming
• forcing nodes to stay on the screen (can cause nodes to overlap)
• history navigation support similar to in a browser (back/forward)
• can be displayed as a widget on other (with a fixed ontology)

Here is a widget version of FlexViz showing the Cell Type ontology:

Currently FlexViz is embedded on BioPortal, which is part of the National Center for Biomedical Ontology (NCBO). FlexViz can also be viewed in a standalone page here.

The source code for the basic graph viewer has been released on SourceForge and can be downloaded there (it is open source).

For more information please contact us.