Caption takes the effort out of finding and setting up the right subtitles. A simple design, drag & drop search, and automatic downloading & renaming let you just start watching. Caption is multi-platform, open-source, and built entirely on web technology.
SubDownloader is a program for automatic find and download/upload subtitles for your movies/series (MKV,MP4,AVI,etc).Discontinued
The software hasn't been updated since 2012 but can still be downloaded.
gSubs is a free and open-source desktop app that finds you the perfect subtitle match for your videos. Just drag and drop the video files that you want to search subtitle for and gSubs will do it's job.