Windows only: While many media players happily play subtitles that are separate from a video, you can still embed subtitles directly into a ripped or downloaded movie file with free utility DivXLand Media Subtitler. With support for over 30 different subtitle formats and 15 different video formats including MPEG, DIVX, and XVID, you’ll rarely come across a combination of subtitle and video you can’t combine. Subtitler made short work of applying English subtitles to the nearly 60 years’ worth of Godzilla movies I threw at it. If it can handle a lifetime of a man in a rubber lizard suit it can definitely handle your foreign film collection. If you find yourself with a big pile of foreign films but a short stack of subtitles, check out recently reviewed Subdownloader to find subtitles for your media. For a solution that adds the subtitles as you are creating a DVD of the movie file, check out this tutorial for DVD Flick. DivXLand Media Subtitler is a free download for Windows only.
Windows/Mac/Linux: Cross platform application Subdownloader makes short work of locating subtitles for your movies. Subdownloader uses a fast hashing algorithm, which, according to the developers, tears through about 4GB of movies per second. The application will search through folders and subfolders and can even handle seasons of television shows. Subdownloader also supports manual searches if you need subtitles for a file or DVD that isn’t stored on your computer. Subdownloader is a free download for Windows, Mac, and Linux (requires Python to run).
Subdownloader [via gHacks]