In my never ending quest for effective, efficient and affordable distribution of (large) media files I gave freecache a whilr. So far I'm astounded! Just add http://freecache.org/ before the url of a file on your webserver and it automatically is added to one or more caches in the 'cloud'.
I tried it oout on a 112 Mb video file, and upon checking today my own link started the downoad from a stanford based cache. Certainly saves me bandwidth, but I wonder if this is a scalable model.
I've added the video as an enclosure in my rss feed, let me know if your aggregator correctly downloaded the file.
PostScript: I ran into a problem adding the file as an enclosure. Most likely Radio UserLand can't figure out the filesize due to the caching mechanism. This sux. There must be a way to add these freecaches as an enclosure.