I recently just randomly came across some cheap airfare for ROUNDTRIP travel between select California cities to/from Hawaii. Best yet, these are for travel in April and May ... which is quite a good deal, considering it's pretty last minute.
The best deals seem to come from San Jose, CA and/or Sacramento, CA to/from the main islands of Oahu and Maui. There may be select deals to Lihue or Kona airport.
Also, other cities including Los Angeles and San Francisco may have some deals.
The roundtrip deals are as low as $177, however, I've found majority of prices to be roundtrip for $189 to $224. That's still AMAZING cheap roundtrip deal in economy.