Sub Station Alpha is a subtitling program for Windows. It is distributed as freeware.
SSA is used via genlock hardware, and is used for real time subtitling. Basic usage is that you watch the video in advance, type up the lines to a file, and then load the lines to SSA. Put a VCR to feed the stuff to genlock's video-in, press buttons to display lines, and SSA adds the subtitles to the video picture, spewn then out of the genlock.
Regrettably, SSA doesn't yet support adding subtitles to digital video (which is a shame from the TV card owner's view, because many TV cards don't have a genlock, and shame from the hardware point of view, because not many people have highly cool video hardware like some SVHS recorders or stuff, but are able to store adequate-quality digital video...)
SSA is a nice program, and wildly popular among Anime fansub community (where it also originated).
Here's my brief experience with it...
I wrote a "script" that had lyrics to one song (Popmuseo by Neljä Ruusua). The scripts can be imported to SSA as a text file that has stuff in form "Name: Text" (Name is the name of the character who says the line - used for informational purposes only).
I started up SSA and imported the text file. I had set the "default start time" to 5 hours. (this is important, otherwise subtitling in real time is hard...) Then I got to the editing mode - ready to start...
Now, I started up the DVD player whence I got the music video and pressed a key to start real-time subbing. For every line of lyrics, all I needed to do was to press space bar. (SSA also has a "karaoke mode", but I haven't tried it yet...)
After this real-time subbing, I edited the script a bit to make the subtitle durations match, Copy/pasted and edited the English translation and changed the appearance a bit.
Since I don't have a genlock, I loaded up the video to VirtualDub (okay, I admit it, captured via TV card because I don't have a DVD-ROM drive either...) and used its subtitling plugin to do the hard work. It reads SSA files just fine.