Your two best options would be
http://www.spreadshirt.com or
http://www.zazzle.com
Both have no minimum order, and both let you create your own shop. They might not be the cheapest options, but they take care of everything for you.
spreadshirt has the most complete solution for your shop, and can be customized the most, but the designs needs to be in the right vector format with only 2-3 colors if you want to print on darker colors
zazzle won't let you customize the shop as much, but lets you create t-shirts with pixel graphic on darker colors. also a lot of other product alternatives.