Yellowstone National Park: This is the National Park Service's Yellowstone page. Here you'll find a history of the park, statistics (the park is larger than Rhode Island and Delaware combined), maps, information about permits, transportation, what to wear in what season, and many other aspects of the Park.
National Park Service: This is the National Park Service's main site. Here you'll find information about all our national parks, as well as lots of policy statements on all aspects of park management.
The Total Yellowstone Page: Created by an enthusiastic private citizen who has visited the park many times, this site has descriptions of his adventures at Yellowstone as well as some impressive nature photos. Don't miss the buffalo pictures.
Yellowstone Net: Another photo-based site, this one by a professional photographer named Russ Finley, who really captures the majesty of Yellowstone. There's also lots of information here. Finley has even put audio clips of wolf, elk, bison, marmot, and geese.
The Yellowstone Wolf Tracker: This site is an entire magazine about wolves in Yellowstone. Re-introduced to the park in 1994, the wolves are thriving. Lots of photos here too.
Yellowstone Fires and their Legacy: For much more on the forest fires that devastated Yellowstone, The Idaho News did a series of stories Yellowstone's past ten years.
The National Interagency Fire Center: The NIFC is government organization that oversees forest fire suppression. Find out about fire ecology, fire behavior, and national forest firefighting policy.