CalFlora Database
- http://www.calflora.org/
- provides access to information about all 8375 currently recognized plants in California, including more than 670,000 plant observations and 20,000 photographs.
USDA PLANTS Database
- http://plants.usda.gov/
- Plant names, photos, fact sheets, and information on culturally significant plants, noxious and invasive plants, and threatened and endangered plants, with links to thousands of plant-related sites and software tools.