I have used Mpix.com in the past and I have always been pleased with the results. Their prints do resist fading for 100+ years. They are fast and easy to use. I have had a few printing issues in the past, but they were taken care of promptly and politely. Their metallic paper is fantastic. It looks beautiful in person. Sign up for an account and try them out!
Be sure you own the copy rights or print rights to the images you are having printed. Basically if you took the photo it is ok for you to print. If a family or friend took the photo you need permission and the same with professional portraits. I know wedding photographers who give their clients a CD of all of the images along with a print right release.
PS I just wanted to clairify, this is not the lab I use for my professional fine portrait art prints. I use a lab that is geared towards professional photographers, my monitor is calbrated to, can print larger items and has more of the varitey that I need. Just an FYI!