Mallard Duck: National Geographic (New Window)
This site has a mallard duck profile as well as fast facts. What to know what a mallard duck sounds like? There is a sound file as well.
The City Naturalist: Mallard Duck (New Window)
This site tells you where to look for Mallard ducks in New York City and also contains some interesting facts about the mallard.
Nature Works: Mallard Duck (New Window)
A nice combination of information and pictures of the mallard duck, Anas platyrhynchos.