By extending Spree Drop Ship to enable supplier payments Spree works as a Marketplace.

PAY.JP makes it way easier and less expensive to accept payments.

Authorize.Net SDK includes standard payments, recurring billing, and customer profiles

Additional Payment Gateways for Solidus

Amazon Payments - Login and Pay with Amazon Ruby SDK

Accepts orders via http, returns payment info via http or streams updates via websockets, stores orders in a DB

[Deprecated] It is recommended to use paypal-server-sdk instead. The PayPal Permission SDK provides Ruby APIs for developers to request and obtain permissions from merchants and consumers, to execute APIs on behalf of them. The permissions include variety of operations from processing payments to...

Launch a landing page on Heroku in less than 10 minutes with JohnHenry. This gem sets up bootstrap and provides Bootstrapped user management pages with Devise. JohnHenry also includes a payment form that works with Stripe and is ready to go immediately.

A straight-forward REST API for Amazon's Flexible Payments Services.

TrueLayer provides instant access to open banking to easily integrate next-generation payments and financial data into any app.This helps easily sign TrueLayer API requests using a JSON web signature.

Accept online payments, create a Platform, and pay out to your sub-entities, sellers and service providers.

To award loyalty points and add loyalty points payment method to spree

This is currently a dummy until a public beta is over.

Add wallet payment method functionality to spree

Spreedly is a cloud service that allows you to store credit cards and run transactions against them, enabling you to accept payments on your website while avoiding all liability and PCI compliance requirements.

A Ruby gem wrapper for the pin-payments (pinpayments.com) API

Experimental library for working with GoogleCheckout. Currently in use for payment at http://peepcode.com.

Spree extension for integration with PayPal Website Standard payment

iDEAL payment gateway (see http://www.ideal.nl and http://www.activemerchant.org/)

A Ruby gem for communicating with the payment platform of Redsys