The following resources can help you Start In Your Yard:

City of Elmhurst: Rain garden cost-sharing programs, rain barrels
Crestview Garden Club of Elmhurst: Encouraging the love of horticulture and gardening through education. Annual (spring) plant sale, including many natives.
Dig Right In Landscaping Inc.: Eco-friendly lawn care and landscaping solutions
DuPage Monarch Project: Increasing monarch habitat throughout the county; formal municipal resolutions; education.
Elmhurst Garden Club: Encouraging the advancement of, and stimulating an interest in, horticulture through education; annual Garden Walk & Faire.
Greenwise: Lawn, garden and landscape design/service
Homegrown National Park: Dedicated to restoring biodiversity and ecosystem function through planting natives and creating new ecological networks.
Illinois Native Plant Society
Illinois Wildflowers
Lady Bird Johnson Wildflower Center
Master Gardeners Illinois Extension: Horticultural experts serving their communities through service projects and educational programs; Help Desk; Wildflower Directory
Morton Arboretum: Encouraging the planting and conservation of trees; education; climate and sustainability
The Conservation Foundation: Preserving and restoring natural areas and open spaces, promoting environmental stewardship; Conservation@Home; native plant guides
U.S. Dept. of Agriculture Plants Database
Wild Ones Greater DuPage: Promoting native plants and natural landscapes