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

Commandline Challenge - Test your command line skills

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.

Prompt - Prompt provides fully-integrated writing education solutions, combining instruction, curriculum, and feedback. We support educational institutions, companies, and individuals.

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

Cwiki - A Command line interface for searching Wikipedia!