If you have an .mp4 or .flv file that uses the H.264 video codec, you can attach the video to any confluence page and allow it to be played embedded inside the page, with the help of jwplayer. I've created two custom Confluence macros for this purpose:

The mp4 Macro

This embeds the mp4 video. It requires three parameters:

1. num (the unique number of this video on the page)
2. height (the height of the player)
3. width (the width of the player)
4. url (the url of the .mp4 attachment)

The flv Macro

This does exactly the same thing as the mp4 macro, but says "Download FLV" instead of "Download MP4".

JWPlayer Attachments

The following attachments are from the jwplayer distribution, and are available via http://static.duraspace.org/jwplayer/