These websites are more useful among tons. I have been delving into Kauai activities info these days. Some websites listed below provide genuine info which is what I am looking for.
Source: http://www.hawaiiwebdesign.com/kauai_activities.htm has categorized activities and listed price associated with each activity so you can compare the info here against your guide book
http://www.livekauai.com/ has web cam for each spot on the map
http://www.trykauai.com/ is similar to the first website but provides some personal touches
http://www.napali.com/ is detailed about Napoli coast
http://www.kauaimenu.com/ provides comprehensive restaurant lists by geography