I second the suggestion of
Azureus. It's a great java client that runs in one window (and only uses one port for everything). When I ran Theshadow or bittornado, it was one window/torrent, which I hated. It also required me to open a bunch of ports on my firewall.
Azureus has everything nicely laid out in one window. It's more towards the type of layout you see w/ a kazaa-type client.