I came out to my brother, whom I hadn't seen or spoken to in twenty years, through Facebook. He "got" the trans thing but thought it was a little weird that I was gay. Whatevah.
I came out to an old childhood friend whom I had also found through Facebook. I didn't know her well after all those years, so I just told her I was trans, not gay. I got back a wonderfully supportive and rambling message that talked about my attraction to women. I friended her after that, so she had full access to my FB profile, where I'm pretty openly into men. I guess now she knows I'm gay.
Here's a funny. Years ago (fifteen?), pre-transition but after I first came out as transgender, I was at a small academic gender conference for TG and IS and all of that. I came out as trans to a total stranger, a curious cis gal who seemed to have just stumbled across the conference by accident. And she said that she was amazed--she would never have guessed that I "wasn't a biological woman." Needless to say, I was pretty pissed, but FTMs were largely invisible then.