FYI!
Both Hawaiian Airlines and U.S. Airways are offering really low fares between HNL-PHX. Price starts at $118 each way with dates from now well into November. No travel from about mid-June through mid-August.

Phoenix/Honolulu $118 each way
Denver/Honolulu $179

Details:
Good availability for April and May travel (some early June dates too). Then again from mid-August through early November. Denver slightly higher for Fall dates.
Use flexible date search to find seats