Apple Remote Desktop: any way to login to multiple computers with one command?

Send the following via the Send UNIX Command, using "root" (sans quote marks) in the "send command" as field:

osascript <<EOF

tell application "System Events"

keystroke "<username>"

keystroke tab

delay 0.5

keystroke "<password>"

delay 0.5

keystroke return

keystroke return

end tell

EOF

Note that the doubled "keystroke return" line is not an error; that's necessary with Leopard, but may or may not be necessary with other versions, so you may need to experiment.

Regards.