http://www.archive.org/details/prelinger

A vast catalogue of downloadable stock footage, Ephemeral Films and even some feature films + an opportunity to submit your own material to the archive.
a very useful site.

Here I'll quote directly from the site ''You are warmly encouraged to download, use and reproduce these films in whole or in part, in any medium or market throughout the world. You are also warmly encouraged to share, exchange, redistribute, transfer and copy these films, and especially encouraged to do so for free.
Any derivative works that you produce using these films are yours to perform, publish, reproduce, sell, or distribute in any way you wish without any limitations''

That sounds pretty good to me.

If you find anything in here that you really enjoy, why not post a link to it
in the Downloadable Media section.