grosser's url_store at master - GitHub
url_store allows you to store any kind of data securely in a URL.
It takes an object, serializes it through Marshal or YAML, hashes it with SHA1 and produces a URL-save gziped string.
example from the readme:
<%= link_to 'paid', :controller=>:payments, :action=>:paid, :data=>UrlStore.encode(:id=>1, :status=>'paid') %>