You might check out the ESRI Geoportal Server product. This is an open source project that was released by ESRI late last year. According to the website:
Esri Geoportal Server allows you to catalog the locations and
descriptions of your organization's geospatial resources in a central
repository called a geoportal, which you can publish to the Internet
or your intranet. Visitors to the geoportal can search and access
these resources to use with their projects.
I would suggest checking out the demo site. The demo site has a map viewer integrated that is based on the ESRI Flex viewer. I think in order to implement that, you have to have the ArcGIS Server package installed. Since this is a Java based open source project, you should be able to switch that code out to implement your own data viewer based on an OpenLayers or similar web map viewer.
I don't know the limitations of this product, but on the surface, it would seem to serve the need to identify your spatial data resources, regardless of format, and potentially be extended to include other spatially enabled layers like from a PostGIS or Oracle Spatial database.