My order (I started HRT 9 months ago)
girlfriend: 6 years ago; took her awhile to deal with it... years. She was finally fine with my transitioning about 10 months ago.
Mom: ~ year ago. At the time I trusted her and felt like I could talk to her about my feelings and transition.
Boss' wife: 10 months ago; I wanted to see how she thought her husband would react.
Boss: 6 months ago; I work for a small company and he's like a good friend. Thought I'd see how he handled before I told the guy who owns the business.
Sister: 6 months ago; see mom...
Final boss/company (lol): 4 months ago; I didn't come out, apparently my boss and his wife thought they would just blurt it out to everyone at diner one night... a diner I wasn't even at... Was pretty mad but my boss felt he needed to tell them. Thinking back it was really good timing. That's the point in HRT where I stopped really passing well as male.
Dad: 3 months ago; he was the person I was most terrified of coming out to but he was moving down to Florida and I was full-time at that point. He took it really well.
Friends/family (facebook): 3 months ago; I was sick of seeing my facebook in "guy mode" and was inspired by a transfriend to just tell everyone. Considering my girlfriend's family is super Southern Baptist conservative, I thought that was going to lead to them disowning her and me. It actually went really well too.
Once you start coming out to people it becomes addictive and once it's over with it is so relieving. It's like having the biggest weight lifted off you chest