MLDonkey. Far too difficult to get it working – this Ferret failed miserably – but definitely worth watching.

‘MLdonkey is a multi-platform multi-networks peer-to-peer client. Originally, it was the first open-source client to access the eDonkey network…Currently, with eDonkey , it supports several large networks, such as Overnet , Bittorrent , Gnutella (Bearshare, Limewire,etc), Gnutella2 (Shareaza), Fasttrack (Kazaa, Imesh, Grobster), Soulseek (beta), Direct-Connect (alpha), and Opennap (alpha). Networks can be enabled/disabled, searches are performed in parallel on all enabled networks, but each file is only downloaded from one network (wait for next release !), but from multiple clients concurrently.’