Lazy Linux: 10 essential tricks for admins

Featuring:

• Unmounting the unresponsive DVD drive (fuser);
  
• Getting your screen back when it's hosed (reset);
  
• Collaboration with screen;
  
• Getting back the root password (booting up in single-user mode);
  
• SSH back door;
  
• Remote VNC session through an SSH tunnel;
  
• Checking your bandwidth (iperf);
  
• Command-line scripting and utilities (for loops, pipes);
  
• Spying on the console (cat /dev/vcsX);
  
• Random system information collection;
  

(From Linux.com)