Active Merchant is a simple payment abstraction library used in and sponsored by Shopify. It is written by Tobias Luetke, Cody Fauser, and contributors. The aim of the project is to feel natural to Ruby users and to abstract as many parts as possible away from the user to offer a consistent interface across all supported gateways.
All sorts of useful information about every country packaged as pretty little country objects. It includes data from ISO 3166 (countries and states/subdivisions ), ISO 4217 (currency), and E.164 (phone numbers). As a bonus it even adds a country_select helper to rails projects.