Yale University
Yale New Haven Teachers Institute: Evolution of Plants
An extensive coverage of the evolutionary history of plants. Click on a topic in the outline and you'll go to a good discussion on this material.
Other
Ny Botanical Garden: Fungal and Plant Diversity
Findings of an expedition by the New York Botanical Garden in French Guiana to investigate vegetation.
Other
Coastal Zone: Plant Evolution
A good slide show which covers the basics of plant evolution. Includes discussion of the major portions of what plants have done to adapt over the eons.
Other
Natural Science: Early Branch of Green Plant Evolution
Recent discovery and theroy that changes the conventional explanation for the evolution of plants.