Pollinator Partnership’s mission is to promote the health of pollinators, critical to food and ecosystems, through conservation, education, and research. They have downloadable eco-region guides and zip code based searches.
Audubon's Native Plant Finder is easy to use. Its focus is on what plants will attract birds in the United States, you can search for flowers, scrubs, trees etc. Just enter your zip code and get started.
Everything you need for finding and learning about Milkweeds native to the Americas. You can search Canada, US or Central America by state or providence. The website now features a Milkweed Podcast too!
The PLANTS Database provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories. Search by state, in addition the website has a trove of information.