And there's Gnutella, eDonkey, Gnutella2, Overnet. Chose one, keep your PC running and let some (selected) people download the full iso. If there are a couple of nodes who have the file you may shutdown the 'root' source, since people can find the file via URLs (ed2k, gnutella, magnet, etc.) on the other sources.

There are Linux programs for at least Gnutella (Qtella, gtk-gnutella) and eDonkey (lmule).

I don't know how much bandwidth you have. It might take some time before a couple of people have the full iso. AFAIK most of these programs/protocols allow partial sharing, so it shouldn't really be a problem if 100 people would want to download the file from PC. If everthing funtions as it should they will 'swarm' eachother to get the partials they haven't got.