University of California
Ucmp: What Killed the Dinosaurs?
This UC Berkeley site extensively covers the death of the dinosaurs. It includes history, theories, invalid hypotheses, and current arguments.
PBS
Pbs Learning Media: Fossils in the Gobi
Biologist Mike Novacek discusses his discovery of mammal fossils in the Gobi Desert and tells us what we can learn from them. From an episode about extinction broadcast on the PBS series "Evolution."