Church institutions were the source of Polish archival materials from the late 12th century.
A subsequent repository was the Crown Archives, from the mid-14th century.
Later, various archives were formed from collections of judicial, district, municipal, and family records. Prussian archives had branches in Poznan and Gdansk. Russian archives had ten branches in Poland, although some were transferred to St. Petersburg. the Galician Archives were mainly in Lwow and Krakow.
Poland GenWeb has good information about obtaining Polish records.
JewishGen also has extensive information about vital records in Poland.