Is there a Ruby library/gem that will generate a URL based on a set of parameters?

Rails' URL generation mechanism (most of which routes through polymorphic_url at some point) allows for the passing of a hash that gets serialized into a query string at least for GET requests. What's the best way to get that sort of functionality, but on top of any base path?

For instance, I'd like to have something like the following:

generate_url('http://www.google.com/', :q => 'hello world')
  # => 'http://www.google.com/?q=hello+world'

I could certainly write my own that strictly suits my application's requirements, but if there existed some canonical library to take care of it, I'd rather use that :).