Aegisub - Aegisub is a free, cross-platform open source tool for creating and modifying subtitles. Aegisub makes it quick and easy to time subtitles to audio, and features many powerful tools for styling them, including a built-in real-time video preview.
Gaupol - Get Stuff Done.
Subtitle Editor - Subtitle Editor is a GTK+3 tool to edit subtitles for GNU/Linux/*BSD.
Time Adjuster - It's Windows application that can: Make your subtitles to appear earlier or later. Convert your subtitle files into other formats. SYNCHRONIZE text with video VERY EASY ! Join & split subtitle files.
Subtitle Composer - A text-based subtitles editor that supports basic operations as well as more advanced ones, aiming...
Jubler - Jubler is a tool to edit text-based subtitles.