How to use the online website of the State Archives of Baden=Wuerttemberg: Lind Street Blog
Online video showing how to use the search function on the website of the State Archives of Baden-Wuerttemberg: Video in German
Geheimes Staatsarchiv: http://www.gsta.spk-berlin.de/ This Berlin archive has some online records.
Das Bundesarchiv: https://www.youtube.com/watch?v=HwjRuw8GBFc
Genealogical sources in the Federal Archive of Germany
Nachlassdatenbank: https://www.bundesarchiv.de/nachlassdatenbank/index.php?sid=6b6fcd2565b00b6893573