VobSub is a plugin for VirtualDub that allows you to rip subtitle files from DVD VOBs and display them with your DivX playback.
http://groups.google.com/group/grk.comp.software/browse_thread/thread/07272150422b014f
http://www.makeuseof.com/tag/how-to-add-subtitles-to-a-movie-or-television-series/