You will not be able to find any genuine US pharmacies that are cheaper than those overseas for brand name drugs. The US pharmaceutical "system" means that most if not all patented products (i.e. new) are going to be more expensive here than anywhere else in the world. Its a different story for generics though. Often US marketed generics are as cheap as you will get anywhere.
If you are buying overseas is probably safer to buy from genuine Canadian pharmacy. Although recently published investigations have shown that most online "Canadian" pharmacies are located in other countries anyway. They offer some Canadian products but that does not mean they are located in Canada.
The best of the US online pharmacies is
http://www.Drugstore.com. I can't give a single recommendation for off shore pharmacies because it does depend on the product you want to buy. In different countries you can buy exactly the same product at quite different prices. You need to do some reasearch and then make sure the pharmacy you intend to use is legitimate. Ring them up, ask for proof of their existence and verify the quality of the product you are buying. Only every use a pharmacy that has been verified in some way. VIPPS for the USA, CIPA for Canada, Pharmacy Checker for any others. Don't buy from
any online pharmacy that doesn't have one of these seals.
Good luck, take care!