Recurpay - Recurpay is a subscription SaaS app for businesses that automates recurring billing.
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.
Stripe Billing Customer Portal - Stripe-hosted page for customers to manage subscriptions
SuperPay - Get paid faster with your own custom payments page
PayPal - PayPal is the faster, safer way to pay online without sharing financial details, send and receive money or accept credit and debit cards as a seller
ServiceBot - The new, open source way to run a business online. Subscription billing, Self-service customer portal, service lifecycle management?