Are you looking for a place that will be cheap, and take care of all of the shipping and stuff for you, like cafe press? Or are you looking for a shop that will print the shirts for you, send them to you, and you take care of the shipping? Sorry if that sounds confusing, it might.
If it's the latter, whenever I design shirts for local bands, I refer them to
http://www.mammothprintshop.com From what I've seen, they have the lowest prices and don't charge a setup fee, and accept paypal. I also know of a few other places, but I'm not sure what you're looking to do. If you have any questions, let me know.