USA

metro / subway systems in the USA:

Atlanta | Baltimore | Boston | Chicago | Cleveland | Los Angeles | Miami | New York City | Northern New Jersey (PATH) | Philadelphia | San Francisco | San Juan | Washington

light rail & streetcar (tram) systems in the USA:

Atlanta | Baltimore | Boston | Buffalo | Charlotte | Cincinnati |Cleveland | Dallas | Denver | Detroit | Houston | Kansas City | Los Angeles | Milwaukee | Minneapolis/St. Paul | Norfolk | Northern New Jersey (Newark) | Oklahoma City | Philadelphia | Phoenix | Pittsburgh | Portland | Sacramento | St. Louis | Salt Lake City | San Diego | San Francisco | San José (Santa Clara Valley) | Seattle | Tacoma | Tucson

special transit systems (monorail, peoplemover, etc.)

Detroit | Jacksonville | Las Vegas | Miami | Morgantown

heritage & classic streetcar systems with regular daily service:

El Paso | Little Rock | Memphis | New Orleans | Philadelphia | San Francisco | Tampa

>>> See also heritagetrolley.org

cities with metro & light rail projects - planned or under construction:

Austin | Honolulu | Omaha | Santa Ana, Orange County

Cincinnati's Abandoned Subway

List of rail transit systems in the United States at Wikipedia

Old Trails - Photos of Urban Rail systems