I'm not up to speed on a lot of Czech beers, but aside from the obvious selections (Pilsner Urquell and Budvar/Czechvar), I found Kozel to be decent enough for the style. Staropramen is OK as well, but sort of seems like a lesser Urquell.

As for Poland, my favourite beer from there is the Okocim Porter that recently appeared on LCBO shelves. Out of the ubiquitous lagers, Lezajsk tends to be my favourite. Zywiec is passable, but not something I buy often. The non-porter Okocim brands I've tried have been awful, as is Tyskie.