Poedit is cross-platform gettext catalogs (.po files) editor. It is built with wxWidgets toolkit and can run on any platform supported by it (although it was only tested on Unix with GTK+ and Windows). It aims to provide more convenient approach to editing catalogs than launching vi and editing the file by hand.
*Unlike other catalogs editors, Poedit shows data in very compact way. Entries are aranged in a list, so that you can easily navigate large catalogs and immediately get an idea about how big part of the catalog is already translated, what needs translating and which parts are only translated in a "fuzzy" way.