Here's a somewhat accurate/inaccurate map of Polish dialects
According to my mom (who I trust more than this map) there are only a couple real dialects in Poland:
Silesian (brown on map) - which is slightly different from "standard" Polish - they have a different word for potato for example. Pronunciation is almost exactly the same - just a tad different.
Mazovian (green on map) - sounds exactly like "standard" Polish with some minor changes. I think they pronounce the letter Ł differently
Kashubian (red on map) - Kashubian - not even a dialect of Polish but rather its own language. I would maybe understand 30-60% of it if I heard it, 70-90% if I read it. Kashubians consider themselves to be both Kashubian and Polish.
Dialect spoken near or around Bialystok (not on map, in eastern green area) - they pronounce things noticably differently from "standard" Polish. Half my family is from there - they speak as though they were drunk and/or Russian. It sounds funny to me.
Gorale dialect (not on map, in the mountains near Slovak & Czech borders) - Totally incomprehensible to me, might as well be its own language. It's something of a mix between Polish, Czech, and Slovak, although it wouldn't be correct to say that the language is "between" Polish and Czech or whatever.
As for me and most people in Poland, we speak the "standard" dialect. I put that in quotes because in Poland its just known as "Polski/Polish"... the de facto language/dialect you learn in most schools around the country. On the map you cound merge malopolski and wielkopolski and parts of mazowiecki and the uncoloured parts of the map.