Just come across this very handy page on the BBC site that lists vocabulary specific to each region of Wales: www.bbc.co.uk/cymru/cymraeg/safle/tafodiaith/. So, whether you’re a Gog or Hwntw, there’s plenty here to give your Welsh a bit of regional flavour. I’ve already decided that I’m not going to refer to the bed as gwely anymore - it’s now the ca’ sgwâr (square field)! 
Diolch yn fawr iawn…I bookmarked this right away.
The link to ‘taifodiaith’ is just brilliant, Have a look at the Valleys page to see the wonderful word ‘Cwmsgwt’ in use. Duw! and there was me thinking that I would never hear or see it again. Cwmsgwt, a kind of ‘Never-Never Land’ for us growing up in Blaenau Gwent…Don’t they use it in Pontypridd to describe all that wasteland up around where Brown Lennox used to be? a version of Y Gwyll for the Rhondda if you like.
Thanks Jon - this is really excellent stuff. It shows what massive variety there is in the vocab of the different regions - sometimes completely different words like “wmed” for face in Ceredigion, etc.