Curiosity Discovery is a website from the Discovery Channel that I found out through Larry Ferlazzo.
People send in their questions and get multimedia accessible answers in return. You can also apply to become an expert to help answer questions, too.
A lot of the entries consist of videos, many of which come together with their transcript, like this one by C. Richard Allen about the death of film festivals because of the internet.
To find more transcripted videos, simply write transcript in the search box.