The TranslateThis Button for WordPress
Now including the TranslateThis Button on a WordPress site is even easier.
Simply install the TranslateThis Button plugin, and use either the widgetized sidebar or template tag to add the button to your blog.
The plugin comes with a wide variety of options that can be easily customized from your WordPress admin section. Includes controls for text & language options, various display settings and other functionality options. See the docs for more info.
Additional language options: