API List - A collective list of APIs. Build something.
Fnd - Browse Apple App Store and iTunes on the Web
Phantombuster - A marketplace of simple to use no-code APIs
JazzMyApp - Let JazzMyApp surprise you with amazing apps everyday. Try it out yourself.
The Unsplash API - No-limits, do-what-you-want API for access to 200K+ HD pics.
Knicket App Search - The future Wikipedia for Apps