Finding OGC WMS, WFS, WCS services

In April, Mike Botts, Botts Innovative Research, Inc. posed a deceptively simple question to an OGC discussion list:  “How does one find existing services that implement OGC Web Map Service (WMS), Web Feature Service (WFS), and Web Coverage Service (WCS) interface standards these days?”   In response to such a fundamental question came an outpouring of responses on the many ways to find OGC services. How many services do you think were identified?