On ambition

I turned 29 last month. There. I said it.
I'm a bit worried, not because I'm getting old(er) but because I thought I would have have achieved more by now. Well, be married with kids or something. Or at least know the direction my life was headed in.
When I was in high school I had a homeroom teacher who made use write down 25 goals at the beginning of the year. The first 5 were short term goals to be achieved by the end of the year. The next 5 were to achieve within the next two years. The next ones within 5 years and so on. Then he told us to write 5 very cool, very fantastic, hearts'-desire goals.
I don’t remember what my Fantastic Goals were (pretty sure there was "own a McLaren F1" in there somewhere though) but I do remember some of my 5-10 year goals clearly. There was Travel the World (tick), Live in London For A Time (cross), Go to Uni and Get a Degree (tick) Get A Well-Paid Career (half tick) and Find the Man of My Dreams (surprising, tick!).
And now that I think about it, that's a pretty good strike rate. So why don't I feel like I've accomplished much? I think it's mainly because I have never had any ambition job-wise. I really, honestly, never had a career in mind when I was growing up. When I left high school, I got such a good OP score everyone expected me to do law or medicine. I balked out of Law at the last minute and did what I had suddenly decided that I wanted to do - Arts (for fun) and Commerce (for practical job-getting). After four years of study, the only things I figured out were a) I hate finance and most forms of commerce; and b) I love Anthropology but not enough to make it a career.
And so I landed by a serious of unfortunate incidents into my current Contact Centre job. Five years later, I feel stagnant, I'm itching to get out and really, really over telecommunications.
But I've got the same damn problem - I don't know what I want to do with my life. I desperately need to find my passion. And pay the mortgage at the same time. I feel adrift, directionless and lacking in ambition. It's so bad I was half-tempted this morning to look at a correspondence course in interior design.
I want to be that woman in That's Life! Who writes in about how she always knew she wanted to be a zookeeper, and now she's caring for giraffes in South Africa or some such. Or the kid who always wanted to be a firefighter, or a doctor and every bit of his education and effort has been bent towards this goal.
I need advice, peoples - how did you figure out your passion? Did you always know what you wanted to do with your life?