They aren't online, but if you know someone with a membership, you can get prints for 0.19 cents apiece.
They are of good enough quality to sell (trust me, I'm a digital photographer and have sold the 4x6 prints in custom greeting cards at art fairs)
Service is quick, and you bring the photos in on CD or flash cards. For the more serious photographers, you can even download and use a custom .icc profile file that EACH lab provides.
They usually can get them done within a couple of hours. Go early and you have a better shot of getting them by the time you're done shopping.
Just remember that here and with any online processor that you're images WILL be truncated. The aspect ratio of digital camera files is different than the aspect ratio of prints. This means you'll get bars cut off the top or sides until the two match. If you have an image editing software you should try cropping to the ratio of 4x6.
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