the Crafting Market in Poland,
I would say it's kind of two different markets. One is the traditional 'folk' arts and crafts which are produced mostly for the tourist and gift trade, the other is the sort of thing people do at home for fun or sale on a very small scale, for example on a market stall. As other posters have said, there are very few dedicated craft supply shops. I've seen a couple of small ones but they didn't have a great range of supplies, but the materials needed for crafting are available in a variety of different places. For example in a haberdashers where they sell thread,yarn, ribbon etc, they usually sell packs of fabric squares for quilting. You can also buy a limited range of craft supplies in Empik, as another poster mentioned. That's a shop a bit like W H Smith in the UK.
Decoupage used to be a big thing here for a while, not sure about now.
There are arts and crafts ideas in some of the homes and interior magazines or in women's mags and there are a few magazines that seem to be mostly knitting and crochet oriented.
The main suppliers for craft materials are the haberdashers, 'pasmanteria' in Polish.
Some of the traditional crafts are the famous paper cutting:
Polish egg decorating, yes people really do this at Easter :)