We are developing a script that is going to allow people to buy a bunch of orders, and we are expecting several hundred to several thousands orders a day. We are going to be ordering things off of sites like Amazon.com, BestBuy and things like that, and it would be alot of work to manually go to each of these sites and place manual orders. So we are looking for some help in doing something where we can automatically place these orders as they come in. We are using PHP but please let us know if yo know of anything to help us.
None of them offer any sort of API that would allow you to purchase through it. This would be an extremely difficult program to write, since it would need to emulate a user, and then fill out a captcha in some cases in order to checkout. You may want to try contacting the websites and see if there is anything they can do to accommodate this type of system. Also, not sure if this has been discussed, but how is the payment going to be handled? This could create some really messy liability if you are taking the payment and then placing the order on your own card, as well as if you are passing the payment information to the retailer.
You would need to give more information about how your are handling the transaction. The most common way to work with the provides you listed is simply affiliate programs. You display the product but hand off the customer for the actual purchase. It doesn't sound like that is your intent tho. If you are open to other vendors you could try Bestbuy - they have a great api that will allow you to actually process the orders depending on your volume. With that said this question is very difficult to answer without a better explaination of how you are processing orders, how many sites you are working with, what sites those are, and the type of eCommerce platform you are using. That's just for starters.
We are running an auction site sort of like Quibids.com. We so, people are winning auctions and we are sending the product to them from the vendor. What we are going to end up doing is buying the product from the vendor and then having the vendor send us the product, we will re box it and send it to the customer. Just, there are potentional to have several hundred if not thousands of auctions won in a day.
If you're still interested in this, we've developed an API (hosted service) for automating orders with Amazon and other popular online retailers (we're adding more rapidly). Please take a look at our site Zinc.io, and feel free to get in touch if you're interested in using it. We're happy to help with your integration!