You can get baby chicks at your local feed store or through your local poultry association. But you might want to order them online through a chick hatchery or supplier. I've compiled this list of chick hatcheries that offer online ordering. Besides baby chicks that grow into chickens, they also offer turkeys, geese, guinea keets, ducks and more.
These are listed in alphabetical order. Pay attention to minimum orders (which refer to chicks only - these vary for other breeds such as ducks, geese, so check the website for info on other minimums).
Cackle Hatchery is located in Missouri and offers more than 185 varieties of poultry, including egg layers, meat birds, bantams, turkeys, ducks, geese, game fowl, rare breeds, Standard Old English, guineas, pea fowl, and more. Their usual minimum is 15-25 birds, but they offer special "city/town" assortments of 5 or 10 birds at a higher price (since shipping fewer birds costs more).
Freedom Ranger Hatchery is a small, family-owned hatchery in the heart of Pennsylvania Dutch country that supplies slow-growing broiler chickens to small farms and organic, free-range, and pastured poultry operations. Their chicken breed, Freedom Ranger, is derived from genetic stock from France and harkens back to American and European heritage breeds. Although their broilers grow more slowly than typical Cornish crosses used in factory farm operations, they are more suited to pasturing, free-ranging, and other alternative and organic growing methods.
Ideal Poultry is located in Texas. They have a minimum order of 25 chicks. They offer bantams, standard laying poultry, ducks, geese, guineas, pheasants and chukar, turkeys, and meat birds.
J.M. Hatchery is a small, family-owned hatchery located in Pennsylvania who offer French Guinea Fowl Keets, White Muscovy Ducks, Khaki Campbell Ducklings, and White Bantam Silkies. Minimum order of 25.