Great news for video publishers that want to expand their possible viewership on YourTube videos, now you can add captions to your videos. From the official blog:
You can add captions to one of your videos by uploading a closed caption file using the “Captions and Subtitles” menu on the editing page. To add several captions to a video, simply upload multiple files. If you want to include foreign subtitles in multiple languages, upload a separate file for each language.
BBC, CNET, MIT, and Japanese anime publisher Gonzodoga are among the partners mentioned in said blog post.
See it in action yourself, just click the menu button in the bottom right corner to turn captioning on.