There is a new photo printing website (similar to Shutterfly or Snapfish) called Artscow. Since they are just getting started, anyone who signs up for a new free account will receive 400 free prints (200 4x6s and 200 5x7s) as well as a free 8x8 photo book (20 pages). You still have to pay for shipping, but it looks like the shipping prices are reasonable. I think with shipping it still ended up being less than 8 cents per print. (It was about $3.99 for shipping 50 prints, the shipping changes depending on quanity). They are only offering this for a limited time until they reach a certain number of registrations. Here is the link to sign up:
http://www.artscow.com/default.aspx?Ref=342180Once at the site, click on the orange button at the bottom center of the page that says "sign up now".
Even after the free prints, their prices for printing photos are cheaper than anywhere else I've seen.