I've never officially had to come out at work. Any of my jobs. I just go into the job like anyone else. If for some reason, who I'm dating or if I'm married or whatever comes up, I'm just honest with them. Very matter of fact. I put up pics in my cubical that make things a little obvious. I have a framed pic of Steven and I in San Francisco. I can't tell you the number of times people ask who he is, or comments. Especially IT guys who come to work on my computer.
Every situation is different, including yours. You come out to co-workers at your own pace, but my advice it just to let it happen naturally.