Our API directory now includes 63 translation APIs. The newest is the TEXTKING API. The most popular, in terms of mashups, is the Bing API. We list 59 Bing mashups. Below you'll find some more stats from the directory, including the entire list of translation APIs.
In terms of the technical details, REST and XML lead the way. There are 43 translation REST APIs and 14 translation SOAP APIs. Our directory lists 38 translation XML APIs and 37 translation JSON APIs.