MacLinguist - A pop-up translator for Mac and Windows that works with any application
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Google Translate - Google's free service instantly translates words, phrases, and web pages between English and over 100 other languages.
Crowdin - Localize your product in a seamless way
Linguee - English Dictionary and Translation Search with 1,000,000,000 example sentences from human translators. Languages: English, German, French, Spanish, and Portuguese
Weblate - Weblate is a free web-based translation management system.