Here's a cool and easy way of adding "on the fly" manual language translation to your SharePoint site using the Microsoft Translator Widget.
1) Go to http://www.microsofttranslator.com/Widget/
2) Enter a site address and site language. (If you are translating from English, you can use http://www.google.com/)
3) Select the desired color and width for your widget, and then select the desired language for translation.
4) Agree to terms and select to generate code. Copy the code displayed in the output box.
5) Paste the code in a Content Editor Web Part on your site.
6) Select the button in the Widget to execute language translation.
English Version:
Spanish Version: