I use AIG Travel Guard and they are EXCELLENT. I found this out when I had to cancel a trip on short notice due to a family illness. Within 2 weeks I had a check from them in the mail for the cost of my plane ticket which was non-refundable.
I recommend you purchase the policy called the "Cruise, Tour and Travel" package. The reason this one is good is because it includes repatriation if you become ill or (god forbid) die while abroad- they will bring you HOME.