I'd say Ibiza, absolutely mad place but dead expensive, at least 40 euros to get into one club (although you won't leave it all night) so doing it on a budget somewhat restricts you. I went to laganas in Zante last year, the place is very clubby, was a decent holiday but not my kinda place (too many english chavs chuckin up everywhere) but its amazingly cheap...Malia is exactly the same as Zante in terms of clubbing