I usually just book mine thru the cruiseline website myself.
I also book my own airline, separate from cruise.
I prefer to have control over my travel times and not leave that up to the cruiseline.
CAUTION: If you're thinking of cruising NCL I would really recommend you use some sort of agency; their own customer service department has left me tearing out my hair (even over minor, minor issues) both times I booked direct. Let somebody else go bald!
BTW, the Pride of Aloha (which does offer a great itinerary and good air inclusive prices as someone else mentioned) is (or was) the sister ship to the Norwegian Sun, which we sailed in '05. Many, many good things to say about it (ask if you're interested). The MAJOR downside is the ships have very little in the way of on-board active recreation (maybe a basketball hoop and ping-pong table). No big deal if you don't do that sort of thing anyway and in Hawaii you're in port everyday. However, if you pay a little more the Pride of America seems to have a few more opportunities for sports and such.
If you decide to sail from the East coast I totally recommend RCCL. Their ships simply can't be beat for what they offer for recreation and activities, especially the Voyager class: ice skating rink and evening ice-capade type show, rock climbing wall, mini-golf and golf simulators, full size sports courts with organized team play, roller-blade track, several pools and hot tubs. Freedom class has all these plus wave rider (think surf boarding), water park for kids and a boxing ring.
We LOVE cruising and over the years I've researched my head off; if you have any specific questions I'd be glad to chime in...

Annette
P.S. For pricing, try comparing what you've found to Travelocity.ca - I've never been able to find anybody that beats them.