Microsoft Bing Translator widget that powers this site was in private beta to invites only, is now released to general public. The widget currently supports up to 20 languages, and with its on-demand nature of the translations, there’s no load on your site and the freshest translations are delivered to the visitor. The translator team’s also planning to add an "automatic" translation functionality, where you can set the widget to auto-translate the page into the visitor's browser language upon arrival. Another interesting feature of the widget is the ability to share a link to the translated page. To manual auto-translate a page just append following code #mstto=es (replace es your desired language code) to the end of the URL you want to get auto-translated.
More info: Microsoft Translator Widget