Here are a few shots from the air which will give you kind of an idea of the terrain that the mushers and their teams are dealing with along the trail.
The Yukon-Kuskokwim Delta
These little serpentine rivers looked like script handwriting from the air.
The mighty Yukon making its way to the sea
Norton Sound
Approaching Nome, which sits right on the banks of the Bering Sea
For some perspective, this is the Iditarod trail map. This shows the restart in Wasilla, but in recent years the restart has been moved to Willow, a few miles to the north where there is more snow and less population. This year the teams took the southern route. The mushers are required to take one 24-hour layover wherever they like, one eight-hour layover at any checkpoint along the Yukon and a final mandatory eight-hour layover at White Mountain. From there, it is approximately 77 miles into Nome, a 10-hour (more or less) run. Whenever we got word that someone was in Safety, we could assume they would be in town in about three hours.
There are 26 checkpoints along the trail where each team is thoroughly checked by the 41 veterinarians who monitor the race.
Wikipedia has a pretty good overview of the race here
http://en.wikipedia.org/wiki/Iditarod_Trail_Sled_Dog_Race