The Printique photo printing service from Adorama has an excellent web interface and the best packaging of any service we've tested, but its prints aren't the sharpest.
RitzPix delivers well-printed photos at average prices, but its web interface is mediocre and processing and delivery times are slower than most services.
Shutterfly offers a huge selection of media on which you can print your photos along with standard prints, but its prices are higher than you pay for the same quality from bargain competitors, especially for larger prints.