Academic Search Premier (EBSCO) - a multi-disciplinary database that provides full text for more than 4,600 journals, including full text for nearly 3,900 peer-reviewed titles. PDF backfiles to 1975 or further are available for well over one hundred journals, and searchable cited references are provided for more than 1,000 titles.
Agriculture Collection - focused on agriculture and its related fields: from practical aspects of farming to cutting edge scientific research in horticulture.
GREENR - global reference on the environment, energy, and natural resources
Public Library of Science - Open Access - a nonprofit organization of scientists and physicians committed to making the world's scientific and medical literature a public resource.
Student Resource Center - offers a mix of resources, including basic overviews of topics.