I use
Shareaza.
I like it, but you can let it monopolize your pipe if you're not careful.
When you connect to another client, either through a search or to actually download, it tells you the program they are using and lets you chat with the user or browse their shared files.
Here's there features splash:
Shareaza is the most luxurious and sophisticated file sharing system you'll find. It can harness the power of up to four separate peer-to-peer (P2P) networks, including EDonkey2000, Gnutella, BitTorrent and Shareaza's native network, Gnutella2 (G2).
Not only that, but Shareaza is completely FREE and won't show any annoying ads or pop-ups. It won't install any unwanted third party programs that can wreak havoc with your computer. No spyware, no registration, no "paid version". Just download and use. Simple.