I'm using ImageKind myself. They're cheap, and they recently added a "StoreFront" thingy. Basically a way to un-uglify the drab and heavily branded default place to sell shtuff (and it's free too!). Anyway, you get plenty of control on mark-up, make a decent commission on framing, and their print quality is good (so is their customer service). All-in-all pretty solid. I've gotta go play with that storefront dealy soon...
Personally, I was comfortable with what they're doing and how they're doing it. And that I can send them full-size TIFFs is a plus too, because, I'm just that paranoid about quality (if I spend hours upon hours getting a gigantic pano print-ready, I definitely want the print to be done using as much information as possible).
Of course, no website will sell your images for you. You need to do that by generating hype and marketing your work. Having a website like ImageKind though can streamline the process of selling your prints. Just point people to that URL and you don't have to deal with the craziness of printing, papers, inks, printers, packaging, matting, framing...and so on. You create, they print.