Universal Subtitles claims that they have " built the easiest way to subtitle videos. Add our subtitling widget to your video (or your site) and click the "subtitle me" button. The rest is simple! Totally free, and no software to download" I saw that it is really easy to use, you select a URL, the video start playing and you start typing. It will wait if you are deleting or stopping, so that you can catch up, and then it will start after a few seconds if you are not typing, so that you can continue. It will start from a few seconds before so you can check what you just typed. Then it provides a very easy way to sync and play and re edit.
The design for entering text is very good and easy to use. However, (there is always a "however", when will the perfect tool be created?) there are some limitations:
1- It will not take any video format, for example, it does not like .wmv
2- You can edit several things but you cannot move or decide where you want the captioning text to show.
3- It places the caption not at the bottom but a little above the bottom, so even if you have left some space for captioning, it will cover the text in the movie, unless you use only one line.. and even in that case it is too high for my preference.
The Chronicle this morning has an article about them and they also talk about Scripto, another one in my list....
Let me know if you give US a try!