Hehe, I've just stumbled across a website dedicated to exactly that problem. I laughed my guts out!
Dutch: Marten Asmodom Vilijn-Mijn naam is Voldemort
Danish: Romeo G. Detlev Jr.= Jeg er Voldemort ( looool! Can you imagine Dumbledore, in a fight against Voldemort, saying "Oh Romeo!" instead of Tom?)
Norwegian: Tom Drodelo Venster-Voldemort den store (Voldemort the great)
Swedish: Tom Gus Mervolo Dolder-Ego sum Lord Voldemort (Ego sum =latin)
French: Tom Elvis Jedusor-Je suis Voldemort
Italian: Tom Orvoloson Riddle-Sono io Lord Voldemort
Spanish: Tom Sorvolo Ryddle= Soy Lord Voldemort
Finnish: Tom Lomen Valedro-ma olen Voldemort
Hungerian: Tom Rowle Denem -???
Czech: Tom Rojvol Raddle-Já lord Voldemort
Macedonian: Tom Redlov = Voldemort (no middle name, no I am, no Lord)
If you'd like to meet Stonne-Stina, or if you want to know what Hermiona Grangerova thinks of a Dooddoener, or why she's into S.H.I.T. , visit
http://www.eulenfeder.de/int/gbint.htm