Lesson 2 - ICND1(1.2) Select the components required to meet a given network specification

The following video is a good introduction to understanding the elements of a network design.  It also describes the various basic topology icons you might run into.

Register for an account at https://learningnetwork.cisco.com. It's the same thing as a CCO account, so you'll need it anyways, and it's free!
Log in and watch the following videos:

The following video goes over a basic network diagram and functions.  Download and take a look at the associated diagram and make sure you understand what is going on.
https://learningnetwork.cisco.com/videos/1144

Lesson 1 - Identify Network Devices in a Topology (Exit to Cisco Website)

https://learningnetwork.cisco.com/docs/DOC-15266

Accompanying Diagram (Exit to Cisco Website)

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 Continuation of the discussion in lesson 1
https://learningnetwork.cisco.com/videos/1168/

Lesson 2 - Characteristics of a Network Review(Exit to Cisco Website)

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The last video reviews the content using a game (Optional). 
https://learningnetwork.cisco.com/videos/1169 

Lesson 3 - Review Game - Who Am I (Exit to Cisco Website)

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Go to the following page http://www.cisco.com/web/about/ac50/ac47/2.html (Exit to Cisco.com). It contains icons for JPEG,Visio and, Powerpoint for creating your network diagrams. If you don't download these Icons now, be aware that this page exists and of its location.

Download the following PDF on the same page and add it to your reference collection. It contains all available Cisco network diagram icons and will help you decode network diagrams provided by Cisco
http://www.cisco.com/web/about/ac50/ac47/PDF_icons.zip (Exit to Cisco.com).

By this point you should have a basic understanding of how to read a network diagram.

Next up, the OSI model.