Biodegradacja Lustrowana Oczami Kamila - A fun-to-navigate picture site with a little of everything - drains, tunnels, abandonments, rooftops and more (in Polish).
Opuszczone - Nicely designed site featuring photo galleries of abandoned buildings around the country (in Polish).
Urban-ator - Abandoned structures, industry, trains and other off-limits places in Warsaw (in English).
Urban Exploration in Poland - Site about abandoned structures, industry, trains and other strange, sometimes off-limits, places in Poland (in English).
Zapomniane Strony - Hard to understand for us non-Polish types, but featuring some really beautiful photos of Polish abandonments and ruins (in Polish).
Zone-A - Histories and wonderful photo galleries of abandoned factories and chemical plants around the country (in Polish).