I have wifi on my 10.04 machine, but I have no use for it. This command will disable it on startup
/usr/bin/dbus-send --system --type=method_call \ --dest=org.freedesktop.NetworkManager /org/freedesktop \ /NetworkManager org.freedesktop.DBus.Properties.Set \ string:org.freedesktop.NetworkManager \ string:WirelessEnabled variant:boolean:false
However, when the machine wakes up from suspend, the wifi comes back on. I have tried to put the above command in a script in /etc/pm/sleep.d but this doesn't work.