I remember reading somewhere that a lot of people used the Bible to learn languages, since it was readily available translated into many languages, and since it was relatively standardized across editions, so a Bible in one language could be easily compared to one in another language. So I looked for a place to find a copy of a Polish Bible online and found http://www.wordplanet.org/pl/index.htm.
But then I got to thinking about other religious texts. I was wondering if one could find a Quran in Polish as well. I found this site that has the Quran translated into several languages, including Polish. You just have to scroll down to find the link to the Polish language version. It is in .pdf form, so you can save it to your computer or tablet as well.
What about other religious texts? I couldn't find the Talmud online, but apparently it has been recently translated into Polish. I couldn't find any information about the Torah in Polish. The Bhagavad Gita has apparently been translated as well, but does not appear to be on the Internet.
And some of the Analects of Confucius are available in Polish as well.