I've always used Murry McMurry Hatcheries. They have a standard order of 25 chicks and now have no shipping fee with the 25-chick order. There is a shipping fee for smaller orders but I always find one or two chicken friends to split an order with me so we can all get the exact number of chicks we want. Plus, now that cold weather is here, shipping with 25 chicks is safer for adequate body heat.
They have a huge selection of chicken breeds and don't have a minimum number of any one breed. I love that I can order 25 different breeds if I want to experiment with something new.
You can look at what they have online or order a free catalog. They also have a large selection of chicken related supplies, equipment, information, etc.
Good luck and have fun!