Have you ever produced a video without adding captions simply because you didn't want to bother using your video editor's clunky, built-in captioning tools? Better yet, want to add captions to someone else's video? Check out Overstream, a service that lets you add text captions to videos from a handful of hosting sites including the big two: YouTube and Google Video.
Diving right in to captioning a video is simple. Once you've given Overstream the URL, it sends you to the Flash-based editor, which at first glance may look complicated, but is about as simple as it gets. If you're used to the timeline controls of any old video player you'll feel right at home--just pick the spot of video where you want to add a caption and start typing away. Overstream will automatically add each caption as a 3-second chunk. If you need to make it shorter or longer, there are toggle controls you can dial up or down, and buttons to send it right next to the neighboring caption.
Additionally, you can see exactly where the caption will end in a color-coded bar that sits below the video's timeline, and tweaking it down to the exact half second or so requires no technical knowhow whatsoever; just drag the bar to the part of the video you want. When finished with any additions you can kick the video back out to Overstream, where it'll be hosted from its original service provider (via embed) while overlaying the captions you've created below.
To test the service, I used the infamous video of Miss South Carolina butchering the question about map proficiency in the United States, and adding captions to the 48-second clip took a matter of minutes. Larger dialogue-heavy segments will certainly take longer, but the editor supports as many captions as you're able to fit. You can view the finished product here.
There are several other captioning services that have done this including BubblePLY, Viddler, and several that have closed up shop including Click.TV and Mojiti. More tech-savvy folks should also give JumpCut a spin, which can do captions on top of its basic video-editing tools.