This was mentioned in another conversation but I thought I'd start a new thread.
A new farmer's market started up last week in Poipu at Kukuiula Village shopping center. It runs Wednesday's from 4-6pm. As well as farmers some of the local shops also participate with samples of their food, and there are a few other food vendors.
Not too popular yet but I think it's going to be a big hit eventually. Great atmosphere and some very tasty treats (like pies) as well as good produce.
Here's a map that shows all Kauai's farmer's markets: