i use photoreflect for online viewing of the proofs by my customers.
they order through photoreflect, which is a turnkey service that will sell, print, and mail the pics to my customers.
you can choose any lab in the US that's affiliated with the photoreflect/labtricity setup-- there are a gazillion.
basically, i upload images, proof the orders when they come in, and photoreflect sends me a check once a month with the profit (they take out their fee and the lab fees). you set your own pricing, so your profit can be pretty good for not having to mess with the printmaking process all that much.
www.photoreflect.com