Command line shortcuts

Clear screen
cntrl l 

ssh connection to unreachable host through a reachable host
ssh -t reachable_host ssh unreachable_host 

set an audible alarm when machine comes online
ping -i 60 -a IP_address

Display top 10 running processes sorted by memory usage
ps aux | sort -nk +4 | tail

save your previous command as a script
echo "!!" > foo.sh

what is my my public ipadress ?
curl ifconfig.me