I hope Harkle.com can keep up. There are four options I have learned about this year for web video captioning:

1. Project ReadOn - lets you submit a video and request captions. http://www.projectreadon.com.
2. BubblePly - lets you make your own "captions" and is not the same thing as professional captioning. http://www.bubbleply.com. The folks behind BubblePly are also working on a similar function for subtitling.
3. DotSub - Subtitling in multiple languages, including English. Videos are posted online for viewing at DotSub.
4. Veotag - Similar to BubblePly and DotSub. Add text to a video. Videos are posted online at Veotag.
   

Now if only Google Video would add a search option for "captioned" or "subtitled." Until they do, you can search video.google.com using "captioned OR subtitled."