Ohio State University
Ohio State Univ.: Gymnosperms (Conifers & Relatives)
A review of conifer biology. Illustrations are great and help clarify the text, which can get a bit advanced for a general audience. A great resource for exam review.
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.
Scholastic
Scholastic: Study Jams! Science: Plants: Gymnosperms: Seeds in Cones
A video and a 7-question multiple-choice quiz on the topic of gymnosperms.