Recurring Billing
Most web app ideas fall under an advertisement model or a freemium model. In the later case, a great application to simplify recurring billing is Chargify. The software lets developers link to a payment form or integrate custom forms with the service through a RESTful API (or a gem).
Once integration is done, administrators can track and update subscribers through a gorgeous web interface.
Overall, the application is easy to use and offers many features over ActiveMerchant. The support team for the application is generally quick to respond and the pricing is reasonable. Looks like a big time saver.
