From AIGA Design Archives, found through Digital Librarian, see below
The sites listed below have extensive listings of image sites, arranged by topic.
These websites contain large searchable collections. Information on any fees for one-time use as well as reproduction rights are described at each site.
The New York Public Library has an excellent Digital Gallery featuring photographs, prints, ephemera (e.g. menus)
Also look at the websites of local museums, magazines, TV stations, etc