The goal of this link collection is to give a brief overview of web pages that might be of help in getting your own researches started. This choice is certainly incomplete and a result of subjective preferences.
Archives / Libraries / Collections
The most important sources for your research are primary sources. The sources of the Polish State Archives can be searched on szukajwarchiwach.
The sources that have been filmed by the LDS - Church of Jesus Christ of Latter-day Saints are searchable in their database using the LDS Filmsearch pages. An annotation because of a frequently asked question: It is a catalog of the microfilmes that can be viewed at one of the LDS Family History Centers, not a direct access to digital church book pages.
The German Bundesarchiv keeps historic German state records and makes them publicly available. They still have the filmed records of the Polish areas occupied in 1939 (the original records have been handed over to the Warsaw Archive of New Records).
The Department of Cartography and Geoinformatics of Eötvös Loránd University, Budapest, Hungaria offers 267 sheets of the Map of Central Europe as of 1910 (scale 1:200 000) for download.
An interesting map can be downloaded from the ambitious Digital Library of the University of Łódź. The Special Karte von Süedpreussen by David Gilly might be of genealogical interest. This map was published 1802-1803. But it shows the borders of South Prussia before the Third Partition of Poland.