I've ordered a bunch of stuff from these guys - nationsphotolab.com, including posters, canvas, metal prints, etc. Excellent quality and the price was right. I was completely satisfied and ready to buy more. Last order was a couple of years ago, though.
I am a photographer and I always recommend mpix.com to my clients who need a good commercial lab. They are the commercial branch of the pro lab I use and they do a really nice job with good color reproduction.