A variety of other documents may be of interest to genealogists. Some documents may be digitized and published on the Internet, but it's more likely that single copies of historical documents live in one physical location. The following is a selected list of document types, but there are many other types of public documents that could useful.
Immigration Records (Ship Passenger Lists)
Local Property Records (use an Internet search engine to search for "[insert your city or county of interest] property")
Legal / Court Documents (use an Internet search engine to search for "[insert your county, district, or state of interest] court records")
Vital Records - Birth, Death, Marriage, Divorce or Annulment Decrees (use an Internet search engine to search for "[insert your city or county of interest] vital records")
Newspaper Archives - Many newspapers historically maintained microfilm archives. Some of these are still housed in newspaper offices, but many have been transferred to local or state historical societies. If known, an Internet search for a specific newspaper title may locate a site that provides information or access. Place quotation marks around the title to make your search more precise (e.g. "Svenska Amerikanska Posten"). If this type of search is not productive, broaden your search to a city or region and search "newspaper archives" or similar phrases.
What other information types can you think of?