Aegisub

If you're regularly working with movie and karaoke subtitles you might be interested in a free subtitle editor featuring built-in real-time video and subtitle preview, besides a the tools required for editing. The name of this free product is called Aegisub.

This is a cross-platform and open source subtitle editor that supports most popular subtitle formats, including Substation Alpha which lets you add text effects, conversion from SRT to ASS subtitles aimed at karaoke effects, among others. Furthermore, besides text effect features, Aegisub comes with a set of powerful tools dedicated to timing the subtitles to the audio as well, including the real-time subtitle previewing.

This application has an attractive and modern design and its accessible interface will let you move between all options and menus with ease. Proceed to the download if interested in finding out more about this dedicated subtitle editor's features.