Oregon State University. A weed ID image collection listed alphabetically by common name (scientific name is also listed).
Rutgers University. Weeds can be searched by common name, scientific (Latin) name, or thumbnail images. This gallery is a collection of photos and descriptions.
University of California IPM program. Key separates weeds into four categories (broadleaf, grass, sedge and cattail). Listing gives common name, scientific name, description, and photo.
University of Illinois. Search by name or plant characteristics.
University of Minnesota. A very basic guide to the common weeds of Minnesota.
Virginia Tech. An aid in the identification of common weeds found in Virginia and southeastern United States. Plants listed by common name and entries contain description and photos.