I found this article good and easy to read, it explains the basic in networking and methods to sniff on a Switch. IMHO this article aims to everyone and is maybe not a must to read but its a interesting topic and well worth checking out.

Source:Linuxjournal
The author's often surprised by how often he encounters network administrators who think their networks are safe simply because the machines are connected to switches. In this article, he explains why that's just not true. The full article can be read here.