Natalie is a work-in-progress Ruby implementation, compiled to C++, by Tim Morgan and contributors.
Natalie can already run quite a few small scripts, which you can find in the examples directory: a small program that brute forces arithmetic for a math game, the ubiquitous recursive Fibonacci script, a GTK hello world example, and so on.
The biggest chunk of idiomatic Ruby code that Natalie has compiled is the Natalie compiler itself (which is written in Ruby), so that's pretty cool! If you've ever wanted to play with a self-hosted compiler, Natalie might be a fun project to get your feet wet!
You can help with the development of Natalie! There are many issues documented on the GitHub project if you want some direction. Or better yet, you may want to try Natalie on a script of your own and see what is broken. Then fix it! :-)