Smithsonian Institution
National Museum of Natural History: Ocean Planet
Detailed website that was a companion to a 1995 traveling exhibit of the Smithsonian. Links to lesson plans and other educational materials are at the bottom of the page. Enter the exhibition to explore the world of the ocean.
Encyclopedia Britannica
Encyclopedia Britannica: Geology: Deep Sea Trench
Detailed information about oceanic trenches, their structure, and how they are formed. Discusses the twenty trenches that exist around the world. Includes several labeled illustrations.
Wikimedia
Wikipedia: Oceanic Trench
Wikipedia provides brief information on oceanic trenches, and has a hyperlinked list of major world trenches.