Open Questions: Plate Tectonics

Galaxy: Plate Tectonics: Categorized site directory. Entries usually include descriptive annotations.

Paleomap Project: By Christopher Scotese. "The goal of the PALEOMAP Project is to illustrate the plate tectonic development of the ocean basins and continents, as well as the changing distribution of land and sea during the past 1100 million years."
This Dynamic Planet: Very detailed map that "shows the Earth's physiographic features, the current movements of its major tectonic plates, and the locations of its volcanoes, earthquakes, and impact craters." From the U. S. Geologic Survey.

Plate tectonics: Article from Wikipedia.
This Dynamic Earth: The Story of Plate Tectonics: An excellent 1996 publication of the U. S. Geologic Survey. This site contains all text from the original document, and has an extensive bibliography for further reading. The book is also available in PDF format.
Tectonic Plates Moved Earlier Than Previously Thought: May 2001 news article from Scientific American about new evidence that plate tectonics began earlier than has been supposed.

Sculpting the Earth from Inside Out
Michael Gurnis
Scientific American, March 2001, pp. 40-47: Motions within the Earth's mantle lead to vertical as well as horizontal movement of continental masses.
The Evolution of Continental Crust
S. Ross Taylor; Scott M. McLennan
Scientific American, January 1996, pp. 76-81: Of the non-gaseous planets of the Solar System, only Earth seems to have retained active plate-tectonic processes. This may account for the current existence of stable continental crust.
Earth before Pangea
Ian W. D. Dalziel
Scientific American, January 1995, pp. 58-63: About 750 million years ago -- 500 million years before the supercontinent of Pangea -- there may have been another supercontinent. Studies of the migration of continental plates utilize magnetization records in ancient rocks.