This board has been so much help to us on our annual visits to Kauai, that I wanted to add a few tips or recs for places I haven't seen mentioned here or deserve that extra praise...I'm not much of a writer, so here just are the facts...
A no name bakery across the street from the Olympic Cafe and around the corner from Shaka Taco has fantastic and reasonably priced freshly baked-on-the-premises danish, cookies, and various breads. They also have coconuts in the fridge and will put straws in them for drinking for $1 or $2.
Carrie Daway - maybe you have passed it on the highway, been hesitant to venture in...It's very bohemian from host/owner to cook, but the people couldn't be friendlier and they do offer freshly caught fish and their 'famous' garlic shrimp (about $13 for a plate lunch).
T&T Steak Burger truck (in the parking lot next to the high end furniture store at the edge of Kapaa. Excellent burgers; as good as Duane's Ono, which we also love. T&T has communal picnic tables and you are at the beach, so unless no one else is there, you'll probably meet lots of nice people too.
-Kilauea Fish Market. We loved their daily fresh fish selection and sauces with rice.
-Tropical Dreams Ice Cream also a video store. By far the best ice cream we ever had anywhere (except for in Italy). All the bins are covered but they will let you see and sample anything. The owner is a trip; a real character.
3) Hanalei -
We always go to the Bakery Cafe in the Kong Lung Center on our first morning, for their macadamia pancakes and egg breakfasts. We also tried their fried chicken once for lunch, which was delicious.
Tahiti Nui - never got to eat there, but had Mai Tais one night listening to fantastic live Hawaiian music and the Mai Tais were superb.
Bar Acuda: I would definitely recommend it for a special occasion dinner. Although it's pricey and the portions are small, the food is very good and they have the best ambience in town in my opinion. Everything we ordered was excellent...be forewarned if you order the scallops, you will get one large scallop and a sliver of another. The lamb actually offered the 'largest' portion' three or four paper thin 'chops'.. All in all though, we ordered many dishes (and ate a ton of their delicious bread and walked away full.
Hamura's Saimin - agreed it's great fun and good food. Nearby, across the street from the Salvation Army (Hamura's is down the street from the S. Army) is a Filipino restaurant (name unknown). When we went there one day for takeout lunch, they were closing and gave us so much free food (in addition to what we ordered), that we had lots of leftovers to eat for a few days.
Finally, everyone knows Costco, but we bought their freshly cut pineapple from Hawaii (most Costcos sell pineapple from Central America), refrigerated it, and enjoyed it all week ..large container at a great price.