Basic Network Information

HowStuffWorks.com is an excellent source for getting good basic information about Networks. It does a very good job presenting the information in a logical organized fashion. These link provide information about networking technologies that is necessary for deploying network test, security, management and monitoring software. Some of the links I like for the basics are listed below:

Howstuffworks "How Ethernet Works
How LAN Switches Work
How Internet Infrastructure Works
How OSI Works

How Firewalls Work
How Routers Work
How WiFi Works
How Radio Works

After you get the basics from HowStuffWorks the about.com is another great resource and you can get more detailed network information from a singe link. It is a great resource that should be bookmarked.
about.com basic networking concepts