Gorm - Gorm .po file editor
Memsource - Manage your translation workflow more efficiently with Memsource.
gted - gted (GetText EDitor) is an editor for gettext po files.
Lokalise - Localization tool for software developers. Web-based collaborative multi-platform editor, API/CLI, numerous plugins, iOS and Android SDK.
Better PO Editor - Better PO Editor is an editor for .po files, used to generate compiled gettext .
Transifex - Transifex makes it easy to collect, translate and deliver digital content, web and mobile apps in multiple languages. Localization for agile teams.