Translate.Net is free client to many language services available online (translators, monolingual and bilingual dictionaries). 43 sites, 55 services, 70 languages, more of 4000 translations directions.

Services:

• Google dictionary and Google translator
• Wikipedia and wiktionary
• Yahoo Babel Fish translator
• SYSTRAN translator (used by Altavista Babel Fish)
• Merriam-Webster dictionary and thesaurus

Full list of languages\services available here

Features:

• intelligent switching of translation directions based on automatic detection of input language and keyboard input language (keyboard layout)
• available portable version
• ability to create user profiles - custom set of services
• history of used language pairs which sorted by last use time
• system hotkeys (Ctrl+C+C and\or Ctrl+Ins+Ins) allow to activate Translate.Net and perform translation from any program easy