Local
AIA - American Institute of Architects - Chicago Chapter
CAF - Chicago Architecture Foundation
Chicago Area Transportation Study
Chicago Career Day
Fredrick Law Olmsted Archives Online
IAA - Illinois Arborist Association
IIT - Illinois Institute of Technology - College of Architecture
Illinois Landmarks Preservation Council
IAPD - Illinois Association of Park Districts
ILCA - Illinois Landscape Contractors Association
INA - Illinois Nurserymen's Association
IPRA - Illinois Parks & Recreation Association
Urban Habitat Chicago
USGBC - United States Green Building Council - Chicago Chapter
University of Illinois - Department of Landscape Architecture
Illinois Department of Financial and Professional Regulation (IDFPR)

Regional
IAASLA - Iowa Chapter American Society of Landscape Architects
INASLA - Indiana Chapter American Society of Landscape Architects
KYASLA - Kentucky Chapter American Society of Landscape Architects
MIASLA - Michigan Chapter American Society of Landscape Architects
Prairie Gateway Chapter American Society of Landscape Architects (based in Kansas and western Missouri) 
St. Louis ASLA - St. Louis Chapter American Society of Landscape Architects
WIASLA - Wisconsin Chapter American Society of Landscape Architects
WLCA - Wisconsin Landscape Contractors Association

National
ASLA - The American Society of Landscape Architects
ANLA - American Nursery & Landscape Association
ALCA - Associated Landscape Contractors of America
The Congress for New Urbanism
CLARB - The Council of Landscape Architectural Registration BoardsThe Cultural Landscape Foundation
EPA's Office of Wetlands, Oceans and Watershed
HALS - Historic American Landscapes Survey
Sustainable Sites Initiative
Urban Land Institute