Top Things To Do in Kauai

For my own reference.

7. Visit Fern Grotto
6. Visit the Grand Canyon of the Pacific
5. Visit Kilauea Lighthouse
4. Visit Manawaiopuna Falls that was shot in Jurassic Park
3. Kayak in Wailua River
2. Watch the ocean spray up to 50 feet in the air in Spouting Horn
1. Access to Napali Coast via the Kalalau Trail, an 11-mile trail that crosses five different valleys and ends at secluded Kalalau Beach

Source: http://www.gohawaii.com/kauai/learn/introduction