SciFinder - Chemistry database. Great resource for water quality and environmental sciences.
GREENR (Global Reference on the Environment, Energy, and Natural Resources) - covers emerging green technologies, environmental impact, sustainability.
National Agricultural Library (NAL) - index to the National Agricultural Library's books, articles, reports, and other materials published worldwide from most recently back to the 15th century. Writings about agriculture cover many aspects of environmental importance. Many resources are available online.
Agricola - Agricultural sciences, environmental sciences, integrated with full-text coverage in the library's other databases.