Have you considered a private YouTube account?
You can upload videos and make them private -- so only you can see them, unregistered -- so only those with the link can see them, or public -- so anyone can see them. Perhaps making them unlisted and then sharing the links with everyone would work? You could have a file that had the title/date of the video beside the link.
Maybe it won't work with rules/copyrights/etc, but that's what I would try to do.
+1 for YouTube link. Also make sure when you share dropbox files or folders, that you are careful about who you invite to the folder. There's two main ways to share something; sharing/inviting to the folder, and sharing a link. Sharing/inviting to the folder let's people change the files, meaning if they accidentally remove the files, it deleted it for everybody else. Sharing the link just takes them to a webpage where they can download all the files, but aren't allowed to change anything.
