One of the things I like about Youtube has been their continued interest in closed captions technology. They seem to constantly be adding small but useful features (such as their interactive captions viewer). Although the number of captioned videos on Youtube is still relatively small compared to the number of videos you can find there, I think that the easier they make things, the more captioned videos we will see.
Described and Captioned Media Program, created a new logo called "Youtube Ready." The logo means that a given closed caption vendor has passed an evaluation, posted their rates, and has a Youtube channel to learn more about their services.
You can see the DCMP's list of approved vendors here. Currently there are 12 vendors on the list.