YouTube has released a new caption feature for videos. As summarized in a recent YouTube Blog posting:

"[W]e've added a new captioning feature which allows you to give viewers a deeper understanding of your video. Captions can help people who would not otherwise understand the audio track to follow along, especially those who speak other languages or who are deaf and hard of hearing."

More in-depth information on the difference between captions and subtitles in YouTube can be found in this article.

An example of captions in a YouTube video can be seen here. Captions can be activated by selecting the "up" arrow button on the bottom right of the video player. Note that captions do not work with embedded videos. They must be viewed at the YouTube site.