If you've spent hours ripping a DVD or downloading a video just to find—when all's said and done—that the audio and video aren't matching up, reader Will suggests using video-Swiss-Army-knife VLC's desynchronisation feature to sync up the audio.
In the VLC Preferences, click on Audio and then tick the Advanced options checkbox; there is an Audio desynchronization compensation setting that allows you to set a positive or negative time delay between the video and audio tracks in milliseconds. I find unsynchronized video/audio unbearable, and have been known to delete files without watching them for it. It never occurred to me that there would be such a simple solution!
Will points out that you need to stop and start the movie each time you make an adjustment, but if you've been banging your head against the wall over poorly synced audio, VLC can make quick work of it. Thanks Will!