Extreme Science
Extreme Science: Challenger Deep
A short description of the world's deepest ocean trench. Includes diagram and map.
Other
Ocean Trenches
A rather detailed explanation of how trenches form and why. No graphics, but some interesting explanations as well as links to other sites and extensive reference list.
Other
University of California: Ocean Drilling Program
Scientists probe the ocean floor off Costa Rica and find evidence that may tell us more about what goes on in ocean trenches.