Just a note on the page you recommend:
http://www.digitaldialects.com/Polish.htm
I've had a brief look at just a few exercises there. Be aware that they are read by a non-native or by a Pole who spent a long time abroad. For a foreigner his pronunciation is excellent. I suspect he's Polish though, because of things like nasal "o" instead of nasal "e" in "łabędź", which is considered incorrect, but typical rather of poles.