Network basics:

http://www.techiwarehouse.com/cms/engine.php?page_id=d9e99072

http://www.lantronix.com/resources/net-tutor-etntba.html

Slide show on Network Basics: http://faculty.ksu.edu.sa/atolba/arabic/PublishingImages/Networking_Basics.swf

Some interesting OSI model urls:

http://www.lex-con.com/osimodel.htm

http://www.protocols.com/protocols.htm

http://www.petri.co.il/osi_concepts.htm

http://studynotes.net/OSI-model

http://www.firewall.cx/networking-topics/the-osi-model/179-osi-data-encapsulation.html

http://compnetworking.about.com/od/workingwithipaddresses/l/aa042900a.htm

http://technet.microsoft.com/en-us/library/bb632418.aspx

http://www.edrawsoft.com/Wide-Area-Network.php

http://www.ratemynetworkdiagram.com/index2.php

vpn: http://www.ratemynetworkdiagram.com/?i=9364

subnet

http://www.freesoft.org/CIE/Course/Subnet/202.htm