For more information on herbicides, as well as weed control practices and concerns, peruse the sites below.

California Weed Identification
University of Illinois — Weed Identification
Illinois Agricultural Pest Management Handbook
Southern Illinois University
Iowa State Weed Science
University of Maryland Weed Science
University of Minnesota Weed Science
University of Missouri Weed Science
Missouri Weed Science For Field Scouting
Montana State Center For Invasive Plant Mgt.
University of Nebraska 2003 Weed Guide
New Mexico State University Weed Science
2002 North Carolina Ag Chemicals Manual
North Dakota Weed Information
Ohio State University Weed Control Guide
Oklahoma State University Herbicides And Use
Purdue National Ag Pest Information System
Rutgers University — Weed Images
Texas A&M — Broadleaf Weeds
Virginia Tech Weed Identification Guide
Organizations And Other Sources
CDMS — Herbicide Labels & MSDSes
Herbicide Resistance Action Committee
Idaho Pest Management Links
International Survey Of Herbicide-Resistant Weeds
Kansas Ag Department Pest Identification Photos
North American Weed Management Association
North Central Weed Science Society
Northeastern Weed Science Society
Southern Weed Science Society
Weed Science Society of America