The BBC's Connecting to the Internet does a good job of explaining the requirements for connecting to the Internet as well as the major media types (including, copper cable, fibre optic, ADSL, and 3/4G). The pages are very detailed and give advantages and disadvantages for each connection type.

Greg's Cable Map is an excellent site with an interactive map showing the location of major Internet backbones across the world. This is a great resource for helping students visualise just how Internet routing works.

BBC Bitesize has a good overview of the differences between LANs and WANs, including some very clear diagrams. It does not cover Personal Area Networks (PAN) though. The very similar GCSE Computer Science page includes both a video and an explanation of WPAN and PAN.

About Tech has one of the better explanations of network cable types, covering the essentials including coaxial, twisted pair, and fibre optic. The hyperlink-studded text makes it easy to students to find out about any related terms or concepts which confuse them.

This short video makes a good lesson starter or discussion prompt. It shows how fibre optic cables used for Internet backbones are laid beneath oceans. This is really useful for showing students that Internet routing is not a complicated or mythical process but, in fact, one which uses relatively basic technology.

This smart-looking Prezi presentation by Phil Bagge is packed full of great graphics and makes a really use introduction to the Internet topic. It takes a clear and visual approach to the idea of a 'network of networks', and really helps students see the structure of the Internet.

This video explains step by step what happens when you enter a URL in your web browser. It covers looking up the IP address using the HOSTS file or DNS, connecting to the destination machine using TCP/IP, and using HTTP to fetch the page. It does a good job of breaking down the process into a series of simple steps that demystify this process for students (hopefully!).

The final part of this BBC Computer Science page deals with issues of IP addressing and routing.