Markdown-based Literate programming in Rust, integrated with Cargo.
See https://github.com/pnkfelix/tango-demo/ for a demonstration of how to use it.
(At some point I hope to document the source code here, but I suspect that I will wait until after I do a rewrite so that the source code actually has some sort of sane basis with a parser or at least proper regexps.)