My website, www.captionpop.com, does this with YouTube videos. It allows you to watch videos with multiple subtitles at once, look up individual words, and buil

My website, www.captionpop.com, does this with YouTube videos. It allows you to watch videos with multiple subtitles at once, look up individual words, and built interactive flash cards out of video snippets. There are also Chrome extensions that do similar things for Netflix. For example, Subadub. Next to interacting with native speakers, I think consuming a ton of media is the best way to learn a language.