Rails_html_output is a project mainly written in Ruby, it's free.
Make Action View produce HTML rather than XHTML
This miniscule Rails plugin stops Rails outputting self-closing (XHTML-style) markup which is useful if you want to use the Rails tag helpers and produce valid HTML.
Works with Rails 2.3 and 3.0.
gem "rails_html_output"
to your Gemfile
.config.gem "rails_html_output"
to your config/environment.rb
.