I came out pretty suddenly just over a month ago. Basically, one of my friends came out, and I felt a lot of internal pressure to do it too. So I came out to my best (straight) friend via email that friday after work, and I told him to tell anyone he liked. I wanted to not be able to hide it any more, because that was so destructive for me.
I came out to my dad the following day while we were driving home from my uncle's house in Bowral. His reaction was not wonderful. He's not homophobic or anything, but the idea really doesn't sit well with him. I've tried to avoid mentioning it to him since then, although I'm not exactly hiding it. I really don't think he was expecting it at all (most people haven't), so the shock would have played some part in his reaction, though it's far from the whole story.
My mum lives in Sydney, and I hardly ever talk to her, let alone see her. I haven't told her yet, though I'm now pretty comfortable with the idea. I think she would have picked up more signs over the years than my dad, so I think it's less likely to be a real shock to her. Her sister was a lesbian, so she might be a bit more comfortable with homosexuality than my dad. But I really can't tell.
I haven't told my 15 year old sister yet, either. She's in a pretty bad way right now, and I don't want to say anything that might make things worse. But on principle, I'd be comfortable with telling her.
The strange thing about coming out is that it can take a lot of work figuring out exactly how you want to do it, what to say, etc. But at the end of the day, the words really come out easily once you start actually saying them, and they don't ever come out quite the way you plan. It's such an awesome feeling, though.