"The Translate Toolkit is designed by localisers for localisers. Its aim is to make your localisation easier and of higher quality.
"The toolkit can convert between various different translation formats (such as Gettext PO formats, XLIFF, OpenOffice.org, and Mozilla formats). This makes it possible to stay in one format across all your localisation, thus allowing you to master one translation editor instead of one per project. Of course an added benefit is that now you cannot create broken OpenOffice.org or Mozilla translation files."
One online service that uses the Translation Toolkit is Open-Tran.eu.