[LeBlanc]

ActiveMerchant is a good one for Rails: http://activemerchant.org/

There are a few for Django, but none that I know of that have the full range that ActiveMerchant does.

Another option is to look for processors with an iframe solution like Stripe Checkout or WePay Iframe Checkout (I think PayPal used to have one but they may have killed it). The nice thing about these solutions is that they take care of 100% of the payment form and annoying stuff like AVS, luhn validation, error response handling, etc.

Good luck! Payments is hard.

[namuol]

ActiveMerchant is good, yes, but I'd really like to avoid sending sensitive customer data through my servers, so server-side solutions aren't really feasible.