The National Geodetic Survey collects data from many CORS sites around the globe for users involved in post-processing their GPS data.  For information about Differential Global Positioning System (DGPS), that which involves "correctors", visit the U.S. Coast Guard Navigation Center Web site at ...
http://www.navcen.uscg.gov/dgps/default.htm

For the DGPS Configuration for all sites visit ...
http://www.navcen.uscg.gov/dgps/DgpsCompleteConfiguration.htm