Gorm - Gorm .po file editor
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.
Better PO Editor - Better PO Editor is an editor for .po files, used to generate compiled gettext .
Weblate - Weblate is a free web-based translation management system.