Chargebee - Chargebee lets you manage subscriptions and payments at scale, handle custom recurring billing scenarios, reduce subscription churn and simplify accounting.

Rainmaker - Rainmaker allows you to make your Google Contacts better.

Chargify - Chargify is the best online billing software for all of your Recurring Billing needs. Learn more about simplifying your Subscription Billing today.

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.

Recurly - Subscription billing and recurring billing management. Recurly offers enterprise-class subscription billing for thousands of companies worldwide.

dip - accountability groups for developers