So I'm not much of a girly-girl, and I am a bridesmaid in my friend's wedding next week. I found a dress that fits me, but I'm not sure about the length — I am 5'3" and not very thin. Where should the dress hit so I don't look stumpy?

I would say right at the knees. You wouldn't want it any longer; it would make you look shorter. And any shorter, wouldn't look good, at least for a wedding.

Right at the knee.

that's my opinion.