Free Protocols Foundation
An independent public forum, dedicated to the support of patent-free protocols.
http://www.freeprotocols.org/
How Internet Infrastructure Works
An illustrated tutorial in a dozen lessons; covers structure, backbone, ip addresses, ports, and more. From HowStuffWorks.com.
http://computer.howstuffworks.com/internet-infrastructure.htm
Protocols.com
Offers a comprehensive listing of data communications protocols, their functions in respect to the OSI model, the structure of the protocol and various errors and parameters.
http://www.protocols.com/