Snagged from a bunch of people: JKR says
Dumbledore is gay. One fan asked whether Albus Dumbledore, the head of the famed Hogwarts School of Wizardry and Witchcraft, had ever loved anyone. Rowling smiled. "Dumbledore is gay, actually," replied Rowling as the audience errupted in surprise. She added that, in her mind, Dumbledore had an unrequited love affair with Gellert Grindelwald, Voldemort's predecessor who appears in the seventh book. After several minutes of prolonged shouting and clapping from astonshed fans, Rowling added. "I would have told you earlier if I knew it would make you so happy."
and JKR
outs Dumbledore She then explained that Dumbledore was smitten with rival Gellert Grindelwald, whom he defeated long ago in a battle between good and bad wizards. "Falling in love can blind us to an extent," Rowling said of Dumbledore's feelings, adding that Dumbledore was "horribly, terribly let down." Dumbledore's love, she observed, was his "great tragedy."
"Oh, my god," Rowling concluded with a laugh, "the fan fiction."
*waits for angsty pining Dumbledore fics*