I follow The Met on Twitter, and I've aqcuired a few followers with the same interests. One follower is a new concept called "Meet me at the Opera", which is a ticket-sharing-social-networking type of thing. It's a really neat concept: you can put ads up if you have opera tickets to share or sell, or just plan to meet a new friend there. I have a profile there under Sarah L, so if you're into opera like I am, perhaps we can make plans to meet there sometime. ;)
I've also discovered via Meet me at the Opera, this fabulous link where you can watch operas!
I'm currently watching/listening to Verdi's Aida at Teatro Regio Torino. Fabulous!