I posted a PodCast bookmarklet last year that turned any old page with MP3 links into an RSS feed with enclosures. takes that a bit further (by running HEAD on each link) to provide the enclosure lengths and MIME types as well. The list of detected file types is long (mp3 ogg mov torrent m4a m4p mp4 mpeg mpg qt avi wav aiff aif mid midi au wmv wma shn flac m3u rm ram), and they also have a proper website (though no database of generated feeds yet).

Webjay's playthispage can do a similar job too, producing an RSS feed with enclosures from a scraped page.