One Hour Translation - Professional translation services for 75 languages on a 24/7 basis.

Transifex - Transifex makes it easy to collect, translate and deliver digital content, web and mobile apps in multiple languages. Localization for agile teams.

Gengo - People-powered translation at scale.

POEditor - The translation and localization management platform that's easy to use *and* affordable!

Translated - Translated is a professional platform that is helping you out with professional language solutions having all the technological resources.

Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.