Can I post video files to the site?
Yes you can. Small files (up to about 8MB) you can upload right through the web inteface. Larger files can be uploaded and then attached ("imported") to any page with the File Import module.
Uploading the large files is a challenge right now because FTP doesn't work in the new clustered environment, but we're working on a good solution for that. Quite possibly it will be elfinder 2.0 when that is released and debugged.
You can also embed YouTube videos into any page very easily. Go to the video on YouTube, grab the "embed" HTML snippet, and paste it into a page.