The Discovery of Global Warming
This is work done under the auspices of the American Institute of Physics.
A hypertext history of how scientists came to (partly) understand what people are doing to cause climate change.
This Website created by Spencer Weart supplements his much shorter book, which tells the history of climate change research as a single story.
There is an associated links page and a references page.
In many ways this is as complete a discussion of AGW as one could hope for with all of the basic and historical science and the data accessible.
You can go as deeply into the field as you like from here, or you can simply read it for the engaging history of the field and how the ideas were developed and demonstrated.
This page is indispensable for scientists and non-scientists alike as a comprehensive introduction to the field.