Read the Docs hosts documentation, making it fully searchable and easy to find. You can import your docs using any major version control system, including Mercurial, Git, Subversion, and Bazaar. It supports webhooks so your docs get built when you commit code. There's also support for versioning so you can build docs from tags and branches of your code in your repository.
Gelato was recently acquired by Mashape and is available as an on-premise option as well as a SaaS offering. It is free to use for open-source projects and has an Enterprise edition available for large scale applications. Pricing for Enterprise edition hasn't been disclosed by Gelato.API Documentation Solutions Gelato