Is there a service that offers me shipping information on demand?

Question

I have multiple buyers and sellers in an app and I want to dynamically calculate the cost (and time) for the most popular shipping providers in the US (FedEx & UPS - DHL and USPS would be awesome too, but not required).

Is there some sort of API that I can use that handles all of that for me? Or do I have to use data services from each shipping provider?

Thanks.

P.S. I will be using Rails.

P.P.S. Any good shopping cart recommendations?

Answer 1

active_shipping gem should be ok for you.

It's used in Shopify.