There have been two major earthquakes in Indonesia recently, one of 9.0 and one of 8.7 magnitude. These are very powerful earthquakes, since the scale for measuring earthquakes is logorythmic not linear, so every increase of 1 in magnitude means it is 10 times more powerful than the previous reading. One of these earthquakes caused the Tsunami that leveled Aceh.
While the earthquakes are terrible and I don't want to appear to minimize the destruction caused by the tsunami, the REAL risk is that there is a supervolcano in Indonesia near the earthquake site that might be showing signs of disruption. The name of the volcano in Indonesia is TOBA. Here is an article from an Australian vulcanologist about the volcano - the Australians have a special interest since they are right near Indonesia and basically would be wiped out if Toba blew up with the force that it has shown previously. The risk is that the recent earthquakes show changes in the fault lines near the supervolcano.
The impact of a supervolcano would be immense. No one knows the real impact but a guess would be that Indonesia (over 200mm people) would be pretty much wiped out along with a lot of the highly populated nearby areas, and agriculture would be severely impacted throughout the region and perhaps the world. The BBC recently ran a show called Supervolcano which I didn't see because I can't pick them up but their site is very interesting.
Just so we don't get smug here in America, we have our own supervolcano in Yellowstone park in Wyoming. Check out the official site monitoring Yellowstone volcanic activity here. There were 97 earthquakes in March 2005 alone! Note that the size of this supervolcano is immense - the caldera (part of the volcano that is typically a cone) is the size of the entire park! They only figured this out when they started surveying Yellowstone from the air and noticed that part of the mountain range had been blown away. Bill Bryson wrote a great book that is highly recommended called "A Short History of Nearly Everything" now out in paperback that describes the immediate effect of a massive eruption of this volcano - even in Des Moines everything would be completely flattened by the blast wave (initial), which would move faster than the speed of sound and just smash everything in its path, then dump feet of ash across the rest of the US and basically make the whole place unliveable.
Yikes! now back to the Illini :)