"This Dynamic Earth" is a U.S. Geological Survey (USGS) publication on plate tectonics, with related links online
geology.usgs.gov/publications/text/dynamic.html

A number of animations related to plate tectonics are found at
www2.nature.nps.gov/grd/usgsnps/animate/pltecan.html

The USGS "GEO-DATA Explorer" is an interactive site that allows you to construct your own maps of many regions, showing topography, volcanoes, earthquakes, and more
geode.usgs.gov/geode_frame.htm

"This Dynamic Planet" (1994) is a reference with global maps of volcanoes, earthquakes, impact craters, and plate-tectonic features
geology.usgs.gov/pdf/planet.pdf

U.S. National Geophysical Data Center data on and images of global relief maps, many of which reveal plate-tectonic features
www.ngdc.noaa.gov/mgg/global/global.html

An archive of articles and data related to plate tectonics is found at
www.platetectonics.com

A variety of geologic animations, including several relating to plate tectonics, can be found at
emvc.geol.ucsb.edu/downloads.php

A starting point for exploring seamounts (underwater volcanoes) is "Seamounts Online"
seamounts.sdsc.edu

Many interactive geology exercises on plate-tectonic and other processes can be found at the "Discover Our Earth" site
www.discoverourearth.org

You can investigate the complex and sometimes bizarre communities of organisms around the vents at seafloor spreading ridges
oceanexplorer.noaa.gov

The Indian and Australian plates were once regarded as one; the story of how they were found to be breaking apart is at
www.columbia.edu/cu/pr/95/18688.html