The Twilio-Rails Ruby Library by Hemant Bhanoo is a Ruby Rails Library for the Twilio API. This library and it's code helps make develop Twilio applications easier in rails. Twilio provides a simple hosted API and markup language for businesses to quickly build scalable, reliable and advanced voice and SMS communications applications.
Transloadit offers media upload, modification, and storage as a service for developers who need that functionality (or, as Transloadit's homepage puts it, "geeks who run web or mobile applications") but don't want to worry about it themselves. There aren't too many moving parts to it, but they're ones a lot of applications make use of. The Transloadit API's main functions include: file upload, image resizing, video file encoding, image thumbnail creations, and file storage on Amazon S3.
Need to make sure your cloud is up and running? If you like pretty charts of that uptime, Nimsoft has got you covered. The company also has a not quite as pretty Nimsoft Cloud Monitor API that allows developers to integrate the tools for monitoring cloud performance into their applications.