Here is a list of some of my favorite things on Kauai:

Breakfast / Lunch

NoKa Grill (Yum!)

Smiley's Local Grinds (Take out only-Dinner is FANTASTIC!)

Lilikoi's

SEA Restaurant

Mariachi's

Dukes

Golf

Hokuala

Puakea

Poipu Bay

Wailua (County Course)

Kiahuna

Makai 

Kukuiolono

Boating / Sailing Trips

Holo Holo Charters 

Blue Dolphin

Kauai Sea Tours

Capt. Andy's

Makana Charters

Beaches:

Kalapaki

Po`ipu

Salt Pond

Brenneke's

Hanalei

Lumahai

Polihale

Ke`e (Permit Required)

Kealia

Anini

Snorkeling locations:

Lawai Beach

Ke`e Beach (Permit Required)

Poi`pu Beach

Lydgate Beach Park

Tunnels Beach

Lehua Rock (Available through Holo Holo Charters and Blue Dolphin)

Salt Pond Beach Park

Anini Beach