The Irish Times seems to think it is Muammar Gadafy
[broken link removed]
Wikipedia and the rest of the world says it is Muammar Gaddafi (al-Gadaffi also)
Here's another one - Muammar el-Qaddafi. It's just a phonetic English translation of his arabic name. I think the one with the Q is the most accurate as his name sounds more like the Q in Qatar.