This is a Babelfish killer if we've ever seen one. AjaxTrans is a multi-language translation tool powered by AJAX.
Authored by Joel Parish, the tool allows you to enter text in English, Spanish, French, Italian, German, or Portuguese, and then translate your text into any of those languages. And, since it's all run using AJAX, the translations appear instantly.
The tool translates your text word-by-word; as you hit the space bar in the upper box, the translation of the word you just finished typing appears in the lower box. Double-clicking in either box flips the translation and the original text between the two fields. Joel has also included drop-down menus to add special characters from other languages. (What the heck is a "?" anyway?)