while there's a lot of new wine countries like australia, new zealand, Chile etc, it's usually best to go with the classic wine countries like france, spain, italy, portugal for supermarket wines. There's a surpermarket wine guide here (Holland) made by a wellknown wine connaisseur which lists hundreds of good to brilliant yet affordable wines, with what to serve them and where to get them. I'll bet there's some similar guide in the US.