Walgreens, Shutterfly, and Snapfish with no problems. I had the release with me when I picked up my prints at Walgreens and wasn't asked for it.
Also, I ordered photo postcards with MOO.com once using some of my Photopass pics. I contacted them via their contact form once I placed the order and provided my order number and told them I could send the release form to them. A very nice CS agent wrote me back and told me it wasn't a problem, that they were familiar with Photopass, knew that a release came with the pictures, and they could tell easily that I had to have purchased the rights to the images to have them at the resolution I had them.