Lokalize - Lokalize is a computer-aided translation (CAT) system that focuses on productivity and performance.
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!
OmegaT - OmegaT is a free open-source translation memory application for professional translators written in Java.
PO File Editor - A FREE online editor that helps you manage translations in PO files for your multilingual software projects.
Gorm - Gorm .po file editor