Overstream allows you to easily add subtitles to pretty much any online video as long as you know its url.
One way that English Language Learners can use this web application is to write direct English translation of videos in their native language. However, that seems to me very time-consuming and not a particularly productive language development activity.
The Bollywood video I blogged about yesterday, though, gave me another idea. Students could pick a video in a language other than English and have some fun creating their own storylines by making up English subtitles for what they see on the screen.