Another one that's been on my list for a long time has now been revealed in Google Earth:
Spaceport America, New Mexico. Wikipedia has its ICAO code as K90NM, which doesn't fit the normal format. RadarBox doesn't know about it - go to Truth or Consequences (KTCS) and head southeast.
EDIT - after ACW's later post, I've changed the filename code to 90NM
Rod