Wow, so this blew up. Figured I'd add something that's been handy for me recently.
It's a browser program not dissimilar to YouTube's subtitle editor that can add captions to embedded videos, but you can also upload/download your own subtitles as well, making it relatively versatile. Then again, I don't know what others want out of community contributions, but for me, it was a pleasant surprise I figured I'd share: