Hmm ;)
I gotta think bout some nice things u should see, but i have no idea which bars/clubs are any good - i'm from poznan and i've never been in krakow and once in warsaw, on airport for like 30 mins:P
Brachson is from AO Legion and he lives in Krakow - ask him on pm; i'll talk with ppl from Warsaw and try to learn smtn useful 4 u.
Oh, and
www.poland.com should have some useful info.