Killbill - Open-Source Subscription Billing and Payment Platform
Plasso.com - Payments made simple. Sell subscriptions & products online.
Subscription Payments by involve.me - Launch a subscription business in one day
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.
Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.
Puddl - Get Complete Breakdown of OpenAI API Usage for Free