Without more introduction, some enhancements that could be implemented for SubDownloader:
-For TV Series: Optionally Track season and episode (support in the backend database needed, of course).
-File renaming (if we know series name, episode and season we can get the episode names online, same for movies, where we can get the movie name online (we can even select the language for the movie in imdb).
-Scan directories but skip files with subtitles already in them.
-Proper upload screen for tv series or multiple files (multiple CDs is not the same as multiple titles)
-Authentication in every upload, so username/pass is kept
-Fix SD for all platforms. Simplify dependencies (include them in package)
-Command-line tool for SD