Jubler is a tool to edit text-based subtitles. It can be used as an authoring software for new subtitles or as a tool to convert, transform, correct and refine existing subtitles. The most popular subtitle formats can be used. Preview of the subtitles in realtime or in design time, spell checking, translation mode and styles editing are some of the main features.
This application has up-to now hundreds of thousands of downloads and is considered the most used Mac OSX open source subtitle editor.
For more information, visit it's dedicated site.