TAO Translator (formerly, The Advanced Online Translator) uses online translation services to provide translations. Currently supported services: Google Translate (supports translation, language detection, dictionary, and reverse translations for single words); Microsoft Translator, a.k.a. Bing Translator (supports translation only); Yandex.Translate (supports translation and language detection); and Yandex.Dictionaries (supports dictionary with synonyms and reverse translations). More services are possible in the future.
HogTrans provides an automatic word translation engine built on statistics of text translations used for free software. It basically provides an automatically created dictionary with multiple translations and example usages for each. HogTrans can import translations from standard GNU .mo-files.