Argentina

Buenos Aires
Cordoba
Mar del Plata
Mendoza
Quilmes
Rosario
Santa Fe

Honorable Mention

Valle Hermoso

Useful terms:
Tram: Bonde
Subway: Subte

While Argentina's only true subway is in Buenos Aires, there are active plans for metros in Mendoza, Cordoba and Santa Fe. Tren urbanos in Tacmon and Salta are also running and function as urban commuter lines.

Argentinian Railway Sites
Argentinian rail blog - great fodder!

Salta Tren Urbano