SDL TRADOS - Computer-Assisted Translation tool, enabling the use of Translation memory.
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OmegaT - OmegaT is a free open-source translation memory application for professional translators written in Java.
Weblate - Weblate is a free web-based translation management system.
Poedit - Poedit translations editor. The best way to translate apps and sites.
Text United - A new, chaos-free way to get translations for your business