Article on Arp Cache Poisoning and Packet Sniffing published in Admin Network & Security on-line magazine.  David J. Dodd president and founder of pbnetworks Inc. discusses how arp cache poisoning on your local network segment works as well as sniffing traffic.  This article covers a number of tools used in arp cache poisoning attacks, including ettercap, arpspoof, nemesis, p0f, dsniff, and scapy.