Crowdin - Localize your product in a seamless way
Poedit - Poedit translations editor. The best way to translate apps and sites.
POEditor - The translation and localization management platform that's easy to use *and* affordable!
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.
Weblate - Weblate is a free web-based translation management system.
Phrase.com - Phrase is a translation management system where localization teams come together to release translations faster and easier than ever before.