I think it's Latoken. I'm not sure if it's popular or not but it's pretty easy to use and very secured at the same time. I recommend it to young ICO projects since there are a lot of active and big traders there.
To be honest, Latoken was not really a good exchange from my opinion, well they rank on TOP 50. But because of a lot project listing at there, the volume trading was really small. Until now i still doesn't use Latoken.
Precisely, I'm not a hater but when I see its poor liquidity it drives me away from using it. I seen many people insanely dump their token in LAtoken, without considering the ico price.
Maybe it will be good if OP will try to at least explain what is really a " small exchanges " mean. Do it literally mean low liquidity or those new ones? Otherwise if we were talking about the popularity well I guess I can't give an answer since I really don't use those.