I'm 25, and even though this would be the "ideal" age to start having kids, I can't see myself having them... for an indefinite period of time. I'd be willing to start thinking about it once I was married, or once I hit 30, but no guarantees there. I feel no need to have my own children, never have... and I think I would only like to have children if I truly WANTED to have them, not out of pressure of any kind.
About five years ago, when I graduated from a Christian university, ALL of my friends got married and now they're starting to have kids galore. They think I'm set on being a "career woman" (since I'm getting my PhD) and that eventually I'll come around to the wonders of motherhood. I think they've been looking for false security blankets their whole lives, and kids are just the next big thing to grab onto. Maybe I will come around eventually, maybe I won't... to me, it should not matter. It comes down to what you and your partner want in the long run, not what society wants.
When ktspktsp and I went rafting on Sunday, we got stuck with a girl scout troop. Mind you, I actually enjoyed hanging out with 3 intelligent, entertaining 10 year olds... and 10 has always been my favorite age of kid to hang out with, if forced to do so. However, I could see myself doing something like scouts or some other youth club once a week or so, and being just as fulfilled (and much more energized) from that as I would be from having my own kids. When I taught high school, I found that job to be very fufilling, and as a result couldn't imagine coming home to a family of my own on top of that daily experience. All of the jobs I've had are very people-oriented, but if I had a family I'd have to come home and continue being other-oriented, cleaning up after them and changing diapers, listening to whining voices and video games, until I dropped into bed, exhausted. Not my idea of a life, though I'm glad others are into it.
Basically I am WAY too selfish to have kids right now, or anytime in the near future, or perhaps for the rest of my life. And I'm fine being that way, actually, and letting people who WANT to be mothers, have that job.