So a quick look at the Kauai Visitor Bureau website and I found some deals that should be illegal. See for yourself: http://www.kauaidiscovery.com/winterspecials/.
Here are some that you should surely take advantage of...
Whalers Cove (http://www.whalers-cove.com/resort.php/WHALERS_COVE/SPECIALS) offers your fifth night free. This is one of the finest condo resorts on the island, perched over the cliffs, you can watch whales migrate from your balcony.
Outrigger's Kiahuna Plantation (OutriggerKiahunaPlantation.com.) has oceanfront condos at $219 a night. Though the property stretches over acres and acres, if you are on the water, you won't feel like you are in a condo complex in Orange County.
Waimea Plantation Cottages (www.WaimeaCottages.com) has 1-bedroom garden view cottages for less than $200. This is one of the better properties on the island; you stay in a renovated plantation cottage, with views of some of the largest banyan trees I have ever seen.
Hanalei Colony Resort (www.hcr.com) is offering 15% off rooms, spa treatments and the Mediterranean Gourmet restaurant in the winter. Want to get away from it all? This is the spot. Your own condo on a beach, yet away from the bustle of any town. This is my choice for a romantic or family getaway.
Grand Hyatt Kauai (www.grandhyattkauai.com.) is offering your fifth night free, a complimentary buffet breakfast and a free room upgrade. This is the granddaddy of Kauai luxury. Get in while you can.
Plus you'll find a slew of activities and other accommodations at a seriously slashed price. If you can get to Kauai, you can stay for less than you've stayed in over a decade.