Libraries tend not to have genealogical vital records, but they can be an excellent source of information about the area plus links, city directories, maps, newspapers, photos, etc.

US
Directory of Genealogical Libraries in the US – Hundreds listed by state with contact information, many with hot links
Allen County (Ft. Wayne, IN) Public Library – Extensive collection of resources and databases for Indiana and the Midwest
Central Connecticut State University – Elihu Burritt Library – Polish collection with a special emphasis on the history of the Polish Americans in Connecticut and New England
      Central Connecticut State University – Elihu Burritt Library – Polish Collection – Video describing the holdings of the collection
Cleveland Public Library – Genealogy SectionLibrary of Congress – European Reading Room
Library of Congress – Polish Directories
Loyola University Chicago – Głos Polek, journal of the Polish Women’s Alliance of America online collection
Michigan – Library of Michigan
Newberry Library – Chicago
Polish Museum of America Library – Chicago

CANADA
Canadian Library-Archives – Genealogy section with links to many topic and sources

GREAT BRITAIN
Polish Library – London

POLAND
Polish Libraries – Contact information for university and other libraries
Polish National Library – Warsaw
Kujawsko-Pomorska Digital Library – Toruń
Małopolska Digital Library – Kraków
Wielkopolska Digital Library – Poznań