I’m using a service that I have used off and on called Fotomoto. If you click on an image page, you should see a “Buy Print” link:
From there, a widget will pop up over the print and you can select sizing, print materials and place your order:

click image to see larger version
I’ve lowered my pricing substantially and hope that for those of you who have asked for a method to buy prints, this will work for you. If it doesn’t, send me an email: photos@blurbomat.com and we’ll see what we can do.
I’m also looking at other services. Fotomoto does good work (if expensive), but they handle the shipping and the processing, so I can lower my prices because the amount of work I have to do to get a print in your hands is decreased.
As always, I’m open to feedback. Please email or comment and I’ll respond where appropriate.
p.s. I’m running a half off sale. Use coupon code: 51B470 for 50% off your order (which can include more than one print and more than one print type) This is limited!
p.p.s. Thanks for your support. It means the world to me.