This volcano is located in Chile, on the border with Argentina in Patagonia (see the map below with volcano, not to scale and enhanced for dramatic effect). The volcano erupted last May and although there was no loss of human life, the town of Chaitén was completely covered in ash and residents were evacuated.
The volcano has once again increased its activity, recently spewing a 6 mile column of ash and causing earthquakes. The Volcanism Blog is posting ongoing reports and photos. El Cordillerano, a newspaper based in Bariloche, also has up to date reports (Spanish only).
The town of Chaitén has been evacuated, although there are some inhabitants who are refusing to leave. Other communities are not in direct danger, although the dust and ash is currently affecting towns 60 miles away. Governmental organizations are distributing drinking water, eye wash and headscarves to disrupted areas.
The volcano could have more far-reaching effects as continued ash eruption and wind patterns could spread dust all the way to Buenos Aires. This dust activity was mild in the city last year and did not stick around very long. The most important consequence for visitors to Argentina is the possible disruption of air traffic for domestic flights if the dust clouds spread and encompass flight paths. Check progress with your travel agent or airline and have a back up plan (options: bus or car rental) in case your flight is cancelled.
Photo from El Cordillerano