Translate.Net is free and open source client for many language services available online (translators, monolingual and bilingual dictionaries). 26 sites, 40 services, 39 languages, 1367 translations directions.

Pros: Trasnslate.Net is a free tool for aggregating results of free language services from Internet into single GUI. It operates like specialized web browser - connect to web sites, query information and then show results in a unified view. The Translate.Net will help you to translate words and phrases to and from numerous languages in a simple way. There are several very popular translating services available online. These include translators, monolingual or bilingual dictionaries. This application acts as a client to several of these services and helps arrive at reliable translation, gives you an opportunity to compare and choose the best options. Currently the application supports some 26 sites with language services, 40 services, 39 languages, 1367 translation directions. That is quite a wide set of resources. These include Google dictionary and Google translator, Yahoo Babel Fish translator, SYSTRAN translator, PROMPT translator and dictionary. Online dictionaries include Wikipedia and Wiktionary, Merriam Webstar dictionary & thesauraus. Encyclopedias and other language services like thesauruses, phraseological dictionary, dictionaries of synonyms and dictionaries of antonyms, etc. are also available.

One can define user profiles and define a customized set of services. History is maintained of last used language pair, this is sorted by last use time. Locale information is cached. When you change the locale the latest used pair of language are selected to make things faster. Use of hotkeys allows users to activate Translate.net and make operating from any program faster.

Cons: Automatic translation is always a little tricky. While freestanding words may get translated quite well but phrases and sentences make the translations difficult. A lot of contextual information is necessary in such translations.

Overall: This is a very good and useful service besides being a free source application. This is clearly at a level of 4 stars.