I saw this and thought hmmm, this could come in very handy. As did 'The Stupid Engineer' As it says in the title, the command is:

for i in `seq 1 255`; do ping -c 1 192.168.1.$i | tr \\n ' ' | awk '/1 received/ {print $2}'; done

For when nmap is just not available. It is pretty slow mind.