Only a few small breeds I'm familiar with:
My parents have a dog that is Pomeranian, Chihuahua, and Mini Doberman Pincer. Very cool dog, but sheds.
A friend has one that is 1/2 Jack Russell Terrior, 1/2 Chihuahua. Doesn't seem to shed, very mellow when indoors.
Grandparents have 2 Bichon Frise's. No shedding, one is a total attention whore/baby, the other is so laid back and cool it's amazing they are the same breed.
The dog I will be getting in the next couple of years is a greyhound. I know you don't want a big dog, but they can be in the high 40 pounds I think (not TOO BIG). Very loyal and sleep alot.....they just like to curl up in a corner somewhere....only thing is they need to run somewhere.
I think any of the small breeds I mentioned are worth looking into, whether pure bred or mixed.