Note that most of what I wrote in http://blog.gingertech.net/2011/06/27/recent-developments-around-webvtt/ is still true – with the exception that IE10’s platform preview 4 now has WebVTT and track support: http://ie.microsoft.com/testdrive/Graphics/VideoCaptions/ and we have started a community group to continue development of WebVTT: http://www.w3.org/community/texttracks/ .