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.

InviteRobot - Instant subscription for paid Slack communities

Killbill - Open-Source Subscription Billing and Payment Platform

SlackPass - Subscription access to anything with Slack

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

Grapevine Surveys - Grapevine is an online survey tool for employee surveys.