For the longest time, my goto for finding APIs was Programmable Web – but that may have changed after perusing Mashape. Mashape isn't simple a searchable directory of APIs, it actually integrates the API directly into their repository. This enables you to sign up, find and test an API without any difficulty at all.
Here's their list of benefits and features:
- Everything in one Place – explore groups of APIs so you can pick, choose, and compare APIs in one place.
- One Credential – Mashape provide you with a credential to access all the APIs consumed in your applications.
- Connect with Developers – built-in messaging and trouble-ticketing system to facilitate communication between developers.
- Try Before you Code – integrated API documentation and test console allow you experience an API without commitment.
- Track API usage – in-depth analytics, reports, errors, and subscription usage of your multiple APIs in one place.
- Multiple Client Libraries – select a programming language and drop the library into your project.
- Instant Distribution – publish your public API and it becomes available to thousands of active developers. You can also add a private API and work collaboratively inside your organization.
- Fast API Doc Editor – create or edit your private or public documentation, enabling developers to quickly understand and consume your API.
- Community Generated Issues – Create, comment, and follow an API issue to report bugs or malfunctions.
- Easily Monetize APIs – Offer public or private billing options. You determine all pricing parameters, such as calls or unique objects; as well as the ability to create multiple plans and feature sets.
- API Status and Notification – view the status of an API, including its average latency and uptime percentage. We send notifications of issues and performance updates.
- Administrative Analytics – number of API calls, adoption rate of developers utilizing your API, and the amount of errors.