It seems that most of the sites offering discount car rentals in hawaii are rising significantly for 2011. The 2010 rates all seemed to be in the $20-$22 range but for 2011 they all seem to be $30 and up.

The best rate I found for my 4 day rental in kauai was using the Hawaiian airlines code at Avis or Budget. About $25 a day plus tax for a compact. Island air codes was a close second.

I bid up to 16 on priceline and got no love. Avis seems better at any higher rate because it has free spouse, no extra fees, and about 3000 FF miles.