Nina, while there may not be dozens of opera/dance/classical threads started on here every day, if you actually read and participate in this board, I think you'll find that there are many people here with a deep, abiding love of all of the performing arts. Not to mention all of the film, tv and pop culture fans on the Off Topic board.
How about this? If you've got something interesting to say about opera or ballet or something else, start a thread on that very subject. And, hell, if it's especially high profile - like, say, an opera production at The Met or ABT's upcoming season, I'm sure you'll find some people here who will enthusiastically pipe in. Just don't discuss any openly bisexual artists or Philly will jump in your thread to claim that they do not exist.