Hello,
there is growing list of programs, scripts etc using OpenSubtitles API.
Good start point is to look to our trac where you can find complete programs list. If you didn't find some application there, which is using API, feel free to add it there.
If you want develop some application, you are free to do so, just follow Notes for Developers. We got for you source codes in many programming languages (15 for now) for creating unique hash codes, you should also read about OSDb protocol.
The most important thing is list of XML-RPC methods