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

fwrdto.me - Send web pages to your email inbox in just one click

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

Jot - The no-fuss way to take notes

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

Noto - Email yourself. Fast.