I'm writing this HTML5 music player that works by dragging music files onto it. (will soon use WebRTC too)
http://pepijndevos.nl/KjuMusic/
It works in Chrome, it used to work in Firefox, and still does on a friends Mac.
However, on my Xubuntu laptop, both with the default and the nightly Firefox, I get
FileList { length=0, item=item()}
when dropping one or more files. I'm not even sure anymore if this is a bug in my code, Firefox, or somewhere else in xfce.