ArcGIS Diagrammer is now available for the newly released ArcGIS 10. The application can be downloaded here from the new code gallery on the ArcGIS resource center.
If you still have ArcGIS Desktop 9.2 or 9.3 then you can still use the previous version available here on ArcScripts.
The most significant change or addition to Diagrammer in the 10 release is the addition of Terrain dataset support. Unfortunately we could not add support for mosaic datasets because they currently do not support xml serialization, that is, terrains are currently omitted from xml workspace documents exported from geodatabases. Diagrammer also needed to be updated to reflect changes to how ArcGIS 10 manages metadata. Overall it is basically the same Diagrammer you love or hate. :-)
If you think that concepts presented in ArcGIS Diagrammer (and other samples like XRay) should be formally ported into the core ArcGIS product then please voice your opinion on ESRI’s ideas forum.