For today's #FreeSoftwareAdvent I'm going to build on @neil list of handy tools for putting together your own media library.
#Aegisub is a powerful editor for .srt, .sub, .ssa, etc. #subtitle files! If you have a video without embedded subtitles and a separate file for the subs, but they don't quite line up, this is for you. Tweak the timing, edit the contents, and see the results immediately on-screen. A life-saver if you import discs in languages you don't speak!