Is there a map of map services somewhere?

Question

I'd like to provide a map based search of map services in a web app.

Ideally, I'd like a web service that displays markers at different zoom levels: local, municipal, county, regional, state or national level. When I click on a marker, I'd like to see a list of urls representing the map services published by that governmental entity.

For example, for a typical state I would expect to see a marker for each county that has public web mapping services. The marker would appear on the county seat, and would contain a url to that counties' map services.

My primary focus is Texas, USA, but any examples of map service map services would be useful.

Answer 1

ONE Geology does this (Europe centric)

Limited USA data - but you can add your own or public WMS links to the map

http://portal.onegeology.org/ (Internet Explorer 7,8,9 only)

More technical details here http://www.onegeology.org/wmsCookbook/home.html

Answer 2

Although not a map, a carefully crafted google search through the API could work wonders:

getcapabilities application/vnd.ogc.wms_xml site:.gov