Ask HN: How are API developers building beautiful documentation?

I'm currently trying to build nice, clean and engaging API documentation for a service I'm working on but have reached a bit of an impasse. As a backend/architect guy I'm looking at things like https://parse.com/docs/rest https://gocardless.com/docs/api_guide and http://documentcloud.github.com/backbone (for example) and they're beautiful!

Is anyone using a tool or CMS to generate these types of API docs (single page w/scrollspy) or are they built in-house with a designers touch?

Would rather be focusing on content over rolling my own, so any help appreciated!