Ethereal has been renamed to "wireshark" and is available in updates as follows:
[root@light ~]# cat /etc/fedora-release Fedora Core release 6 (Zod) [root@light ~]# grep wireshark list wireshark.i386 0.99.4-1.fc6 updates wireshark-gnome.i386 0.99.4-1.fc6 updates
You might want to check the wireshark faq for more details.