Check out the travel deals on this site. This can make a great Diving Vacation or any vacation for that matter that much better. Deals on airfare, hotels, car rentals, cruise packages, tours and vacation packages.
I just ran a trip through MLT vacations so I thought I would compare. At this site it was almost 400 bucks more expensive and had a stop in Charlotte.
I did the same thing on a trip we have going... it was over $700 higher for 2 than what our travel agent got us.
but if you want cheap outta the cities you can't beat (MLT) and their red hot deals, this is what my wife and I usually use (although, not for the above mentioned trip). Worryfree is a bit limited on where they go, but you can always get to mexico or jamaica, sometimes puerto rico, and others.
Also, orbitz.com, cheaptickets.com, and travelocity are usually very good.
Fred