The recently launched API for Google Translate makes it easier to add translation options to any web application. A Google Spreadsheets gadget uses the API to translate the text from a spreadsheet. The input text should be in English and the destination language should be specified in the settings. To add the gadget to one of your spreadsheets, click on the Insert drop-down, select Gadget, go to the Custom section and paste this address:
The gadget can be embedded in any web page and it updates the content every time you republish the spreadsheet. There's also an option to automatically re-publish a spreadsheet when changes are made.