http://ogc.dmsolutions.ca/

This is local a mirror of the schemas from the OGC schemas repository at
http://schemas.opengeospatial.net/

If you are looking for the schemas to use for MapServer 4.2 and older then
download the file schemas-mapserver-4.2-and-older.tar.gz

MapServer 4.4.0 and more recent uses the exact same schema tree as
schemas.opengeospatial.net, so you should either point your mapfile's
ows_schemas_location metadata to http://schemas.opengeospatial.net/ 
directly, or setup your local schema repository.  To setup your local schema
repository you can either download directly form 
http://schemas.opengeospatial.net/ or get the latest 
schemas.opengeospatial.net-*.tar.gz file on this server.

More details in the MapServer WMS-Server-HOWTO and WFS-Server-HOWTO at
http://mapserver.gis.umn.edu/doc.html