Read on Mail - Why "read it later" - email yourself now ⚡

Lago Billing - Open-source alternative to Stripe Billing and Chargebee

Noto - Email yourself. Fast.

Metronome - Metronome helps software companies launch, iterate, and scale their usage-based business models, with billing infrastructure that works at any size and stage.

Captio - Captio enables companies and their employees an improved control of their expenses and the discovery of new savings opportunities. 

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