Ruby has Opal http://opalrb.org/ a Ruby compiler to JavaScript.

Or Decaf http://trydecaf.org/

Or http://rubyfiddle.com/ if you want to be literal about Ruby in the browser :-)

Thanks. Brython looks more like what I was looking for. Everyone's porting code into Javascript but I think a better browser can be built with more language support.

Brython: http://www.brython.info

Thanks, that's more of what I was looking for.