From Nikolaj Lynge Olsson:Subtitle Edit is an editor for movie subtitles. With Subtitle Edit you can easily adjust the start time of any subtitle if it is not synchronized with the movie.

The features are it converts between SubRib, MicroDVD, Substation Alpha, SAMI, youtube sbv, and many more, cool audio visualizer control – can display wave form and/or spectrogram, import and OCR VobSub sub or idx binary subtitles, and can open subtitles embedded inside mp4 or mv4 files.