We recommend you a publication titled “Narodowe Archiwum Cyfrowe. Wizja, projekt, ludzie.” (National Digital Archive. Vision, project, people.) published on-line by the NDA on a Creative Commons License. This publication is also accessible via the Digital Libraries Federation thanks to Silesian Digital Library and Maritime Digital Library.
Beside visitng National Digital Archive, please check also http://szukajwarchiwach.pl/ website which allows to search in resources of Polish National Archives.