Ask HN: What other SASS for developers (like Zencoder and Twilio) are out there?

I'm trying to think of new projects to start on and I think some of the best possible ideas are taking the existing professional APIs that I can pay for, like Zencoder and Twilio, and use them to make something really cool and useful for small businesses, online and in my local area.

So, with that said, I know that there are other startups like this out there, providing really great tools and infrastructure that I can use for my own.

Are there any, even your own, out there that you can recommend?