These links will take you directly to the portions of databases that contain materials relevant to Biology. However, this is by no means an exhaustive list. Feel free to explore the General Collections to find additional resources.
College Open Textbooks is the initiative of a number of organizations who have made it their goal to provide free, open source textbooks online for students.
The Global Text Project is a joint initiative between the Terry College of Business at the University of Georgia and The Daniels College of Business of the University of Denver to publish eBooks that can be accessed by all, especially the developing world.
InTech publishes more than 2,300 open textbooks and 6 journals in a variety of subjects that fall under the heading of science, technology, and medicine.
Hippocampus offers educators a wide variety of multimedia content online, including videos, animations, and simulations. An additional feature offers educators the ability to create "playlists" for their students, which correlate specifically to their particular instruction material.