AjaxTrans is an online translator which can translate between English, Spanish, German, Italian, Protuguese, or French. Best of all, this is using AJAX so the translated words will be immediately shown on the other text field:
Start typing any text you want to be translated into the green field. The words should be automatically translated into the language of your choice and appear in the bluish box. To switch langauges, simply click on the language you would like to translate from and then procede to select the language you would like to translate into. In order to swap the contents of the two boxes, use a double click.