Well, I'm done at 36. I have a ds12, dd9, and a 2 month old. I honestly think your 30s is a great time to have kids. I'm much happier, we are better off financially, and I have alot more patience now. In my 20s, I was so worried about what everyone else thought, keeping my house clean, etc. Now, I'm happy just to sit and look and my little one. And she is no afterthought-dh and I talked about having another baby for 9 yrs. The time just seemed right last summer (when I was 35). I finally feel like our family is complete, and I had a tubal right after delivery.
For others, I think anytime up to 50 would be ok.