Imagine if you could add thoughts and notes to a YouTube video to make it useful and instructive, rather than just fun and time-waste-y. Overstream, a new video subtitle web app, aims to help you do just that. Find a YouTube or Google video you want to annotate, copy the URL, and load it into Overstream to bring up a simple but effective interface that adds readable words at any point in the video. You can make the resulting video public or private and export the subtitles for use in video editing suites. Besides being a useful tool for adding your thoughts to intriguing presentations (or just viral videos), it’s a nice replacement for the similar but defunct Mojiti. Overstream requires a free sign-up to use.