This is how I make cartoonish female torsos. I thought this might be helpful to some people. I break it down into two main shapes: an upside down triangle for the rib cage and a diamond shape for the hips. I like firmer body types, so the edges are rather sharp and simplified -- not much of a waist or fleshy bits. I like the pinup girl figure ^.^
If you change the size of one or both of the main shapes, then you can alter body types.
I made one for the boys....but then it occurred to me that my males are more like lithesome ballerinas than muscle dudes. Also, I tend to exaggerate males a lot more than females. So, for now, I'll just leave the girls.
There are tons of other ways to do this and this isn't for realistic people or anime. I just thought I'd show this to you and you might get something from it :3
EDIT: Wow! This piece is really popular! If there's any kind of guide/resource you would like to see me do, please leave a comment!