B&H is the best place to buy film, photo, digital, and video online. They have outstanding service and do not screw people over. What's more, they have some of the best prices. I have ordered from them at least a dozen times without any problems whatsoever.
No store screws all their customers, but Adorama screwed me both times I ordered from them. One time they sent me short dated and outdated film when I paid full price. The next time they backordered stuff that they claimed they had in stock when I placed my order causing me to miss a deadline. Avoid Adorama. It's not worth risking a huge headache to save $5 on a $200 order. The only reason to ever order from Adorama is if B&H, Calumet, Cameraworld, and Beachphoto are out of what you want, or if you are buying an Adorama branded product, or ordering a kickass Microdear microfiber cloth.
Calumet, mentioned by Blacknet, enjoys a very good reputation, but I have not used them lately.
Some stores have B&H's level of service, but at a slightly higher price. I think Calumet falls into that category, so does
www.cameraworld.com (Camera World of Oregon, the largest distributor on the West Coast). They enjoy a great reputation and I ordered from them a few times a few years back with great service. Do not order film from them because they cannot compete with B&H for film prices and they will usually tell you that if you ask. Cameraworld will often pricematch B&H on many things which makes them a great choice if you live on the West Coast and want your stuff fast. They also have a cool open box and returned item section that usually has great deals.