There is - after all - a Petstore implementation for Ruby. Somebody asked a question at the DZone and the response posted by Raphael Valyi was:

Re: Is there a Pet Store in Grails/Rails?

I'm speaking here for the Rails (JRuby) side:
there is actually a petstore, it can be found there:

Some guys used it to compare C-Ruby vs JRuby performance: