Linux: Using the "kill" command to terminate processes
Linux: Using the "ps" command to see what is running on your system
Networking: How to decipher netmasks (subnet masks)
Networking: Using arp to find MAC addresses
Networking: Using netcat to print from Linux to a jetdirect printer
Networking: Using netcat to transfer a file
Networking: Using ssh to tunnel tcp connections
Networking: Using telnet to diagnose a mail server
Networking: Using the ping command