It is very difficult to understand people here, they speak too quickly.
A coach from Salta takes about 12 hours and costs about 80 pesos, however it is difficult to get one at sensible hours, ie you have to either leave stupidly early or arrive stupidly early, the best I could find was 6pm - 6am, and the bus was an hour late, which suited me fine.
Being a central hub for the Chaco country, the bus terminal in Resistencia has many connections per day with Buenos Aires (12 hours), Rosario (10 hours), Puerto Iguazu (12 hours), Salta (13 hours) and Asuncion in Paraguay (6 hours). Lesser served routes (ie. once per day) include Cordoba, Posadas and Rosario. There are numerous local buses to the neighbouring town of Corrientes and the National Park Chaco. The bus terminal is located outside the town center: Taxi rides between downtown and the bus terminal cost around 10 Argentinean Pesos.