Party Central.
Okay it doesn't come for free. You'll certainly spend more time/money than you wished, but if you are looking for some fun try these are great places to start
European Islands: Greek Islands, Spanish Islands and the Turkish Coast
Honduras: Utila Island
Thailand: especially the islands and Bangkok
Philippines: Boracay
Carnival (the week before Lent): The best parties are in New Orleans (USA), Barranquilla (Colombia), Northern Germany, Port of Spain (Trinidad), Brazil or Santiago de Cuba (this one is over the summer)
Jamaica: Negril is the spot, but watch out for crowds though, they can get overwhelming
Indonesia: Head straight to the Gili Islands