From Paris you have the choice of the two flag carriers, LOT and Air France. You could try a travel booking site such as Expedia to see which has the better deals around your chosen dates.

www.skyscanner.net is a site which lists low-cost carriers. It does not show Krakow at all but suggests that there are flights from Cologne to Warsaw (though it didn't actually list any for the random dates I tried!). Warsaw to Krakow is about two-and-half hours by train. Polish friends tell me it is an easy and comfortable journey.