Subtitle Fixer allows you to interactively adjust subtitle files which are out of sync with their corresponding video files.
To adjust a whole subtitle file, identify a line of dialogue in the film (a 'reference point') using the video window, then using the built-in search function, locate that line in the subtitles. Click "Set from video" as the line is spoken, and the whole subtitle file will be adjusted. If the subtitle frame rate is also wrong, just repeat the procedure for one more line of dialogue (using the 'additional reference point') and the problem is fixed.
Subtitle Fixer supports SRT subtitle files for all video types, and SUB subtitle files for AVI videos.
Subtitle Fixer is a Qt4.x app using the Phonon/VMR-9 backend, and relies on this to display the subtitles in the video window. This works for Windows, but hasn't been tested on other platforms.