PLANTS Database
A single source of standardized information about plants, maintained by the USDA. This database focuses on vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories.
CalFlora
Information about more than 8,000 currently recognized vascular plants in California, including scientific and common names, synonymy, distribution from literature sources, legal status, wetland codes, habitat info, and more. Includes a photo of the plant, if available.
Oregon Flora Project
A group at Oregon State University that is working to produce an up-to-date list of Oregon's native and naturalized vascular plants.