We recommend! Overstream.net is a new website which allows you to add subtitles and captions to any of the videos you find on YouTube, Google Video, MySpace video, and Daily Motion. In order to use this application you must make a profile and have Java Script, Cookies, Flash Player 8 and the Overstream Editor on your computer. Once have all these tools on your PC, than you are ready to add subtitles to Online Videos. Fot Tutorial Check here
In their own words:
“Have you ever wanted to customize an online video by adding your own comments or subtitles in any language, or wanted to send a custom video postcard?
All of this is possible with Overstream: using our online Overstream Editor, you can easily create and synchronize your subtitles to any online video*, store them on the Overstream server, and send the link to the subtitled video overstream to your friends.â€
Also try Babel Bear (http://www.babelbear.com)
You can add subtitles directly on top of YouTube videos and request subtitles for videos that don’t already have them.
TransYouTube.com also provides subtitles for YouTube videos. You can add/edit subtitles for the videos.
When watching a video on YouTube just change the URL address from youtube.com to transyoutube.com and you can enjoy the video with subtitles if available, or you can add a new subtitle.
http://www.subsedit.com
It helps to write subtitles to YouTube videos for free and without any registration and question.
You can just start putting youtube video url.
There are also few other functions for srt subs.