Docs.rs – documentation hosting for the Rust ecosystem

Very exciting! Per-platform docs (platform dropdown in the doc section), a built-in source browser, a rendered copy of README.md (if present), semver compatible URLs, documentation for previous versions, and probably other things I haven't found yet. Looks like there's an about page under the "Rust" menu:

https://docs.rs/about

The backend is, of course, in Rust. :)