I think Swanson maybe the best. Their quality is consistently high, their prices are at least as good as Amazon's and sometimes way better, and they have lots and lots of house brand products that are really excellent.
As an example, they offer a formula to help you sleep that is very effective and downright cheap. Since I am an insomniac this has been a big help. Of course what often happens is that I get a good two hour nap, but believe me, when you have a hard time sleeping, even that can be a boon.
They are always offering promotions too. This one gives you $5 off your first order, and I get a kickback too. So check 'em out, I think you will like them. And I would love to hear your feedback!
PS. I got an unexpected package the other day which turned out to be a fine demonstration of Swanson's integrity. I had bought some Ceylon cinnamon in capsule form. A little back story: The stuff you buy in supermarkets that is labeled Cinnamon is actually Cassia, a relative that taste a lot like the real thing but is actually a cousin. Since real cinnamon has beneficial qualities, ie, helps to regulate blood sugar, you want the real thing. Well it turns out Swanson had sent me capsules of Cassia that were mislabeled and they sent the real thing to correct their error, with a letter of explanation and an apology for their error.
The point of course is that a company with less integrity would have been glad to sell you the cheaper Cassia as cinnamon. The taste differences are so subtle that unless you have a highly trained palate, you wouldn't notice. So, good for Swanson! http://www.swansonvitamins.com/referral/friend.html?id=d311473d-8ab1-430f-b004-e9c9012b234d