US Geological Survey
Usgs: u.s. Atlantic Continental Margin Gloria Mapping Program
This site from the U.S. Geological Survey allows you to access detailed images of the continental margin around the United States. There is additional information about the sonar methods used, and a wealth of additional sources listed.
University of Washington
University of Washington: Coastal Processes and the Continental Margin
Events affecting the continental margin off Washington State are presented. This article comes from the "Thompson Times," an onboard newspaper from the UW's primary research vessel, the Thomas Thompson.
Other
Aligarh Muslim University (India): Active and Passive Continental Margins
Explains what active and passive continental margins are and where they can be found. Includes a world map showing their locations.
CK-12 Foundation
Ck 12: Earth Science: Bathymetric Evidence for Seafloor Spreading
[Free Registration/Login may be required to access all resource tools.] Describes features of the seafloor and how they are mapped by echo sounding. It touches upon the continental margin as well.
Other
Geo Man: What's the Difference Between an Active and Passive Continental Margin?
Explains what active and passive continental margins are and where they can be found.