Pootle - Multiple file formats.
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Crowdin - Localize your product in a seamless way
Poedit - Poedit translations editor. The best way to translate apps and sites.
Dictionary.com - Dictionary.com is the world’s leading digital dictionary. We provide millions of English definitions, spellings, audio pronunciations, example sentences, and word origins.
Weblate - Weblate is a free web-based translation management system.