QR Codes are 2-d bar codes.
Install Plugin
./script/plugin install http://qrcode-rails.googlecode.com/svn/trunk/plugins/qrcode
Usage: qrcode(url, pixel size, type_number, id_of_generated_div) e.g.
<%= qrcode('http://www.google.com/', 2, 8, 'my-qrcode') %>