A bon vivant at the bar I used to hang out at gave me the best cure. It works 99.9 % of the time, and it is simple. Balance a full glass of water on the top of your head. Remember that it has to be hands free, but you can keep them nearby just in case.
I once had to go to the hospital after a 14 hour hiccoughing jag. The doctors in the ER all had a good laugh at my expense and then one of them cured me. I had had my hair cut the day before and a few small (tiny) pieces of hair fell into my ear and were pressing up against the Vagus nerve (I think that it may be the nerve that brianjedi was refering to). He floated the hair out of my ear with some saline and presto - no more hiccoughs. After 14 hours the relief was fantastic.